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.
Merge pull request #163 from benjchristensen/rx-0.10

Upgrade to RxJava 0.10.0