Major Description
The json spec says that / must be escaped as \/, see http://json.org/ for example.
To reproduce:
{{velocity}}
#set ($map = {'a': 'a/b'})
$jsontool.serialize($map)
{"a":"$escapetool.json('a/b')"}
{{/velocity}}
results in
{"a":"a/b"}
{"a":"a\/b"}