JVMCBC-89: Depend on RxJava 1.0.3

Motivation
----------
Amongst other enhancements, RxJava 1.0.3 has a critical enhancement
that allows cancellation of not-running tasks which have an impact
on timeout() operators. It is Java >=7 only, but important, since users
were already running into it.

Change-Id: I41d88a6b01dabcb7cef7bf965a796c300b846f6b
Reviewed-on: http://review.couchbase.org/44481
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Simon Baslé <simon@couchbase.com>