Improve ROME feed reader tests
Update ROME feed reader support

This commit replaces the Android ROME feed reader with the rometools
variant of ROME version 1.5. This requires dependency updates and
modifying imports to account for the different package name.

See http://rometools.github.io/rome/index.html

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