Upgrade to Selenium 2.15.0

v2.15.0
=======
Project:
  * Code donation from Google.

WebDriver: 
  * Now supports up to Firefox 11.
  * Changed order of FirefoxProfile initialization attempts on a
    remote host: 1) try to load from capabilities, 2) try to load
    locally if webdriver.firefox.profile is specified, 3) create an
    empty profile.
  * Added the beginning of infrastructure for gathering logs from
    webdriver tests.
  * Added an UnreachableBrowserException.
  * Additional work on the WebDriver JS console.
  * Implicit waits now change how long we wait for alerts. This
    functionality will change in 2.16
  * FIXED: 2700: The infamous scrolling issue.
  * FIXED: 2816: ClassCastException when calling switchTo().alert().

Grid:
  * Grid now distinguishs between CLIENT_GONE and
    FORWARDING_TO_NODE_FAILED.
  * FIXED: issue where older RCs could not connect to a newer hub.

RC:
  * Selenium-backed WebDriver now uses atoms for typing.

Automation Atoms:
  * Significantly reworked input device abstractions.