cleaned up closing of input/output streams

deleted duplicated URLConnectionHtppClient.close(Closeable) in favor of
InternalUtils.close(InputStream) and InternalUtils.close(OutputStream)
thereby avoiding the reflection when searching for a flush method

also removed package private InternalUtils.toString(Reader) and moved
code to public InternalUtils.toString(InputStream) to be able to close
only the inputstream
added support for gzipped content

URLConnectionHttpClient now sets both Host: api.twitter.com and
Accept-Encoding: gzip headers to tell twitter we'd like gzipped
responses.

URLConnectionHttpClient.getPage2 then gunzips the response content if
the header Content-Encoding: gzip was received.
error page now correctly gunzipped if needed
Merge pull request #6 from azonli/gzip-encoded-responses

Gzip encoded responses, thanks to Azonli