visually distinguish operators that use schedulers; add distinct doOnEach diagrams
Async conversions
Use Object as argument type for fromFragment helper

This is to prevent compilation failures in projects that do not link the support-v4 library. The only other option I saw to fix this would have been to split up the android module into one for native fragments and one for support fragments, which I found would come with unjustified overhead. Hence I settled for the cheap way, which is to sacrifice type safety here.

Refs https://github.com/soundcloud/RxJava/issues/2
Add scala adapters for doOnEach operator.
tests for zipping a finite and an infinite Observable
Remove unnecessary cast.
Adding utility functions for observables of strings useful for processing non blocking IO.
Moving StringObservable to contrib module
moving the AssertObservable class to the test side of the build.
setting the up that string test to use core test
Removed spurious package
Moved Subscription object to package rx.lang.scala.subscriptions with the other subscriptions
Added immediate scheduler
Added new thread scheduler
Added current thread scheduler
Added ExecutorScheduler
Added ScheduledExecutorServiceScheduler
Added ThreadPoolForComputationScheduler
Added ThreadPoolForIOScheduler
Deleted old scheduler factory methods.