RxJava 0.18.2

Pick up ReplaySubject fix as discovered for Hystrix 1.3.16 release
Merge pull request #260 from benjchristensen/rxjava-0.18.2

RxJava 0.18.2
Compilation fixes

... missed these when doing https://github.com/Netflix/Hystrix/commit/00d8ecb9c87c35e91a2b1a696ea92c8ffb8121ad#diff-bcc766d81acc427070683ec44e8320c2
Merge pull request #262 from benjchristensen/compilation-fix

Compilation fixes
New signature for HystrixObservableCollapser

Replacing mapResponseToRequests with functional style selectors and allowing streaming response from Observable.
Javadoc for new HystrixObservableCollapser methods
Merge pull request #261 from benjchristensen/observable-collapser

New signature for HystrixObservableCollapser
[Gradle Release Plugin] - pre tag commit:  '1.4.0-RC4'.
[Gradle Release Plugin] - new version commit:  '1.4.0-RC5-SNAPSHOT'.
Version 1.4.0 Release Candidate 4