0.2.RC2

Added a new consumer.unsubscribeAndDisconnect() method.

This release includes the current Java 7 compatible version of OkHttp: 3.12.1.

Development notice: Gradle was updated to a recent version (4.4).

I decided to keep the bit older version of OkHttp 3.12 since OkHttp 3.13 is incompatible with Java 7 / Android 4

Thanks to @victorbucutea for providing a PR with most changes already included.