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
As for the minimum API level, I remember there was a discussion around this back when RxAndroid was a contrib module to core. People seemed to agree then that we should support Gingerbread, however, there are no formal checks in place to verify that we're using appropriate framework APIs.

We should probably add static analysis around that, although this might prove tricky since the linter might not work with non-Android projects?

Keep in mind that the code above will never fire in production. It's for debugging during dev time. Do you still see value in optimizing this potentially at the cost of backwards compatibility? Thanks for pointing out `[Array]Deque` though, I wasn't aware these were superior choices in this case. Is this because of complexity for random access, or why exactly?