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.