Merge pull request #246 from kriswuollett/no_fin_on_closed_stream

Stopped sending final empty frame on stream initiated in sender half-closed state.
Don't use IOException APIs not in Gingerbread
Merge pull request #247 from square/jwilson/new_ioe

Don't use IOException APIs not in Gingerbread
Added contentType/Encoding to HttpResponse's Entity.

Clients should expect that OkHttpClient HttpResponse Entity's contentType
and contentEncoding are not null when the headers are present.