Added support for Request Cache and Reactive Execution
Do Not Reschedule Callbacks

- Use `Immediate` so that we don't add scheduling overhead unless needed.
- Reuse the Hystrix thread if it is there. The computation of the callback can be part of the Hystrix thread.
- No one using Hystrix+Observable should be doing anything blocking on those callbacks.
Semaphore vs Thread Isolation

- only SEMAPHORE reject if SEMAPHORE isolation is being used
- unit test to assert that THREAD and SEMAPHORE isolation reject independently of each other
Merge pull request #238 from benjchristensen/semaphore-vs-thread-isolation

Fix for Semaphore vs Thread Isolation Bug
Merge pull request #230 from dmgcodevil/master

Added support for Request Cache and Reactive Execution
rxjava-core:0.17.2
[Gradle Release Plugin] - pre tag commit:  '1.4.0-RC2'.
[Gradle Release Plugin] - new version commit:  '1.4.0-RC3-SNAPSHOT'.
Version 1.4.0 Release Candidate 2
rxjava-core:0.17.3
Add missing reset for CommandExecutionHook in HystrixPlugins.UnitTest#reset
Update servo to 0.6
Merge pull request #243 from dmuino/servo06

Update servo to 0.6
Merge pull request #240 from chrisgray/bug/resetCommandHook

Add missing reset for CommandExecutionHook in HystrixPlugins.UnitTest#re...
Fix for issue #241 (leaner error propagation in hystrix javanica)
Merge pull request #244 from dmgcodevil/master

Fix for issue #241 (leaner error propagation in hystrix javanica)