Revert "Update ROME feed reader support"

This reverts commit 0c51342d0965e3c767dc8615cbb60659a33c6ef5.
Improve ROME tests

Additional testing revealed that the rometools version of ROME is not
compatible with Android. The Android port of the ROME feed reader was
reinstated in the previous commit. See the open issues against the
rometools project for more details.

https://github.com/rometools/rome/issues/155
https://github.com/rometools/rome/issues/163

This commit adds more complex tests for RSS and Atom feeds which verify
functionality that fails with the newer ROME version.

Issue: ANDROID-50
Add OkHttp ClientHttpRequestFactory implementation

This commit adds OkHttpRequestFactory which can be used as an
alternative to the native HttpUrlConnection or HttpComponents clients
provided by SimpleClientHttpRequestFactory and
HttpComponentsClientHttpRequestFactory.

Issue: ANDROID-138
GitHub: 10, 12