Upgrade to Jackson 2.6.0

#137: Allow filtering content read via `JsonParser` by specifying `JsonPointer`;
  uses new class `com.fasterxml.jackson.core.filter.FilteringParserDelegate`
  (and related, `TokenFilter`)
#177: Add a check so `JsonGenerator.writeString()` won't work if `writeFieldName()` expected.
#182: Inconsistent TextBuffer#getTextBuffer behavior
 (contributed by Masaru H)
#185: Allow filtering content written via `JsonGenerator` by specifying `JsonPointer`;
  uses new class `com.fasterxml.jackson.core.filter.FilteringGeneratorDelegate`
  (and related, `TokenFilter`)
#188: `JsonParser.getValueAsString()` should return field name for `JsonToken.FIELD_NAME`, not `null`
#189: Add `JsonFactory.Feature.USE_THREAD_LOCAL_FOR_BUFFER_RECYCLING` (default: true), which may
  be disabled to prevent use of ThreadLocal-based buffer recyling.
 (suggested by soldierkam@github)
#195: Add `JsonGenerator.getOutputBuffered()` to find out amount of content buffered,
  not yet flushed.
 (requested by Ruediger M)
#196: Add support for `FormatFeature` extension, for format-specifc Enum-backed
  parser/generator options
- Minor improvement to construction of "default PrettyPrinter": now overridable by data format
  modules
- Implement a new yet more optimized symbol table for byte-backed parsers
- Add `JsonParser.Feature.IGNORE_UNDEFINED`, useful for data formats like protobuf
- Optimize writing of String names (remove intermediate copy; with JDK7 no speed benefit)

#77: Allow injection of 'transient' fields
#95: Allow read-only properties with `@JsonIgnoreProperties(allowGetters=true)`
#222: EXTERNAL_PROPERTY adds property multiple times and in multiple places
 (reported by Rob E, thatsnotright@github)
#296: Serialization of transient fields with public getters (add
    MapperFeature.PROPAGATE_TRANSIENT_MARKER)
 (suggested by Michal L)
#312: Support Type Id mappings where two ids map to same Class
#348: ObjectMapper.valueToTree does not work with @JsonRawValue
 (reported by Chris P, pimlottc@github)
#504: Add `DeserializationFeature.USE_LONG_FOR_INTS`
 (suggested by Jeff S)
#624: Allow setting external `ClassLoader` to use, via `TypeFactory`
#649: Make `BeanDeserializer` use new `parser.nextFieldName()` and `.hasTokenId()` methods
#664: Add `DeserializationFeature.ACCEPT_FLOAT_AS_INT` to prevent coercion of floating point
 numbers int `int`/`long`/`Integer`/`Long`
 (requested by wenzis@github)
#677: Specifying `Enum` value serialization using `@JsonProperty`
 (requested by Allen C, allenchen1154@github)
#679: Add `isEmpty()` implementation for `JsonNode` serializers
#688: Provide a means for an ObjectMapper to discover mixin annotation classes on demand
 (requested by Laird N)
#689: Add `ObjectMapper.setDefaultPrettyPrinter(PrettyPrinter)`
 (requested by derknorton@github)
#696: Copy constructor does not preserve `_injectableValues`
 (reported by Charles A)
#698: Add support for referential types (ReferenceType)
#700: Cannot Change Default Abstract Type Mapper from LinkedHashMap
 (reported by wealdtech@github)
#725: Auto-detect multi-argument constructor with implicit names if it is the only visible creator
#727: Improve `ObjectWriter.forType()` to avoid forcing base type for container types
#734: Add basic error-recovery for `ObjectReader.readValues()`
#737: Add support for writing raw values in TokenBuffer
 (suggested by Guillaume S, gsmet@github)
#740: Ensure proper `null` (as empty) handling for `AtomicReference`
#741: Pass `DeserializationContext' argument for `JsonDeserializer` methods "getNullValue()"
 and "getEmptyValue()"
#743: Add `RawValue` helper type, for piping raw values through `TokenBuffer`
#756: Disabling SerializationFeature.FAIL_ON_EMPTY_BEANS does not affect `canSerialize()`
 (reported by nickwongdev@github)
#762: Add `ObjectWriter.withoutRootName()`, `ObjectReader.withoutRootName()`
#765: `SimpleType.withStaticTyping()` impl incorrect
#769: Fix `JacksonAnnotationIntrospector.findDeserializer` to return `Object` (as per
  `AnnotationIntrospector`); similarly for other `findXxx(De)Serializer(...)` methods
#777: Allow missing build method if its name is empty ("")
 (suggested by galdosd@github)
#781: Support handling of `@JsonProperty.required` for Creator methods
#787: Add `ObjectMapper setFilterProvider(FilterProvider)` to allow chaining
 (suggested by rgoldberg@githin)
#790: Add `JsonNode.equals(Comparator<JsonNode>, JsonNode)` to support
  configurable/external equality comparison
#794: Add `SerializationFeature.WRITE_DATES_WITH_ZONE_ID` to allow inclusion/exclusion of
  timezone id for date/time values (as opposed to timezone offset)
#795: Converter annotation not honored for abstract types
 (reported by myrosia@github)
#797: `JsonNodeFactory` method `numberNode(long)` produces `IntNode` for small numbers
#810: Force value coercion for `java.util.Properties`, so that values are `String`s
#811: Add new option, `JsonInclude.Include.NON_ABSENT` (to support exclusion of
  JDK8/Guava Optionals)
#812: Java 8 breaks Class-value annotation properties, wrt generics: need to work around
#813: Add support for new property of `@JsonProperty.access` to support
  read-only/write-only use cases
#820: Add new method for `ObjectReader`, to bind from JSON Pointer position
 (contributed by Jerry Y, islanderman@github)
#824: Contextual `TimeZone` changes don't take effect wrt `java.util.Date`,
  `java.util.Calendar` serialization
#826: Replaced synchronized HashMap with ConcurrentHashMap in TypeDeserializerBase._findDeserializer
 (contributed by Lars P)
#827: Fix for polymorphic custom map key serializer
 (reported by mjr6140@gitgub)
#828: Respect DeserializationFeatures.WRAP_EXCEPTIONS in CollectionDeserializer
 (contributed by Steve G, thezerobit@github)
#840: Change semantics of `@JsonPropertyOrder(alphabetic)` to only count `true` value
#848: Custom serializer not used if POJO has `@JsonValue`
#849: Possible problem with `NON_EMPTY` exclusion, `int`s, `Strings`
#868: Annotations are lost in the case of duplicate methods
- Remove old cglib compatibility tests; cause problems in Eclipse
- Add `withFilterId()` method in `JsonSerializer` (demote from `BeanSerializer`)