Merge branch 'release-0.6.0' into dev
Push version to 0.7.0-SNAPSHOT.
Update to retrofit 1.6.1.

- https://github.com/square/retrofit/blob/master/CHANGELOG.md#version-161-2014-07-02
Allow customization of RestAdapter.

- Pre-build a RestAdapter by simply overriding `newRestAdapterBuilder()`.
- Set the log level on an existing RestAdapter instead of rebuilding it.
Merge branch 'rest-adapter-customization' into dev
Add okhttp, -urlconnection 2.0.0 as optional dependencies.
Fix README line breaks.
Prepare version 0.7.0.
Change log for 0.7.0.
Replace self-closing `<p/>` with `<p>`.
Merge branch 'release-0.7.0'