Upgrade to RxJava 0.10.0

- RxJava 0.10.0 changes from onError(Exception) to onError(Throwable) so I want to get that in before releasing Hystrix 1.3 as I don't want a breaking change like that to affect Hystrix once released.
- Hystrix itself still exposes public methods using Exception so if a Throwable is caught internally it will be wrapped inside an Exception. Changing to Throwable is not worth breaking backwards compatibility and revving to Version 2.0.

NOTE: This won't build against Maven Central quite yet as RxJava 0.10.0 is not yet available there. I'm building against internal Netflix repos while getting Hystrix 1.3 ready for release.