JVMCBC-67: Upgrade RxJava to 1.0.0 GA

Motivation
----------
RxJava just released 1.0.0 GA, and since this codebase was on release
candidates before this commit makes sure to run the latest version
possible.

Result
------
Depending on RxJava 1.0.0 GA

Change-Id: Ic27826524a546630f23adfe345bd8ffcd6b692b9
Reviewed-on: http://review.couchbase.org/43366
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>