Added GenericStringBuffer::GetSize() within unit test, as in 0.1x branch.
Added GenericStringBuffer::GetSize() within unit test, as in 0.1x branch.

git-svn-id: f2a605aed50f4b2fdced9f156cca822d7a53f72e@61 c5894555-1306-4e8d-425f-1f6f381ee07c

zhengxle/rapidjson,zhengxle/rapidjson,zhengxle/rapidjson