Subject based event bus (rxandroid-eventbus)

This is a long standing thing I meant to pull out of our app which has proven invaluable for us. It's just a thin wrapper around Rx subjects, but with an API that lends itself well for dependency injection.

Sample activity:
https://github.com/ReactiveX/RxAndroid/pull/60/files#diff-18

Sample service:
https://github.com/ReactiveX/RxAndroid/pull/60/files#diff-19
nit: doesn't need fully qualified.

There's a setting in IntelliJ to fix this:

![screen shot 2014-11-19 at 10 02 18 am](https://cloud.githubusercontent.com/assets/66577/5111133/343e9d3a-6fd3-11e4-8ce1-613aa9f08199.png)