fixes issue couchbase/couchbase-lite-android/issues/214

By setting the size of the underlying data on InputStreamBody at construction time, and returning the value in getContentLength(), this allows apache HTTPClient to send attachments to the server unchunked. Sync Gateway can handle chunked data but the current release of CouchDB (1.5.1 tested) can not.
Merge pull request #217 from couchbase/feature/couchbase-lite-android-issue_214

fixes issue couchbase/couchbase-lite-android/issues/214