Bump to Robolectric 2.3, make samples build under Studio 0.8.+

refs https://github.com/Netflix/RxJava/pull/1449
Fix issue #1522
Restore use of SpmcArrayQueue in RxRingBuffer

- Modification of SpmcArrayQueue with fix from https://github.com/JCTools/JCTools/issues/21
- Restore RxRingBuffer to use SpmcArrayQueue
- this reduces object allocation significantly (see pull request for screenshots)
Merge pull request #1526 from benjchristensen/ring-buffer-queue

Restore use of SpmcArrayQueue in RxRingBuffer
Failing unit test for reduce, showing it does not implement backpressure correctly
Added another unit test to OperatorReduce/backpressure
Add operators to create Observables from BroadcastReceiver

it allows to listen global and local (with support LocalBroadcastManager) broadcasts
remove main thread unsubscribe, fix LocalBroadcastOperatorTest
fix sticky intent duplication, add tests for OperatorBroadcast
Optimize the fix for takeLast and handle the race condition
Fix the unbounded check for merge
Make "single" support backpressure

Signed-off-by: zsxwing <zsxwing@gmail.com>
Merge pull request #1530 from zsxwing/issue-merge

Fix the unbounded check for merge
Merge pull request #1523 from zsxwing/issue-1522

Fix issue #1522
Merge pull request #1528 from Yarikx/android-broadcasts-rebased

Add operators to create Observables from BroadcastReceiver (rebased)
Merge pull request #1527 from mattrjacobs/reduce-fails-on-backpressure

Failing unit test for reduce, showing it does not implement backpressure correctly
Concat Backpressure

Route backpressure through the inner subscribers.
Fixes https://github.com/Netflix/RxJava/issues/1480
Amb with backpressure support
Propagate request(n) to each AmbSubscriber

... and then keep propagating to the winner.
Merge pull request #1533 from benjchristensen/issue-1516

Amb + Backpressure