Revised version of Android UI component operator
Drop use of WeakReferences and use a custom subscription instead
Drop volatile in favor of failing fast if not subscribed from UI thread
Only release references in unsubscribe

We decided it's better to leave it to the caller when it's appropriate to release, cf. #1
Add guards around log statements
Remove isFinishing check when calling back to activities

We decided it's sufficient for the callback to be safe as long as the caller unsubscribes in onDestroy
Implemented the 'TimeInterval' operator
Implemented the scheduler version of the 'Return' operator
Updated the comments
Fixed issue #417
Fixed testOnErrorViaHasNext in issue #383
Removed the unnecessary 'catch' and 'fail'
Blocked 'hasNext' instead of 'next' until any notification arrives
Followed the iterator contract
Force 'hasNext' and 'next' throw the error once they have already thrown it before
Fixed issue #454
Renamed the log tag as it was too long
Singularize AndroidObservables, move to observables package
Merge pull request #459 from zsxwing/issue454

Fixed issue #454
Merge pull request #458 from soundcloud/android-ui-component-operator

[rxjava-android] OperationObserveFromAndroidComponent