0.4-beta: for Kotlin 1.1.0-beta-18

• Switched to Kotlin version 1.1.0-beta-18 (republished version).
• CoroutineDispatcher methods now have context parameter.
• Introduced CancellableContinuation.isCancelled
• Introduced EventLoop dispatcher and made it a default for runBlocking { ... }
• Introduced CoroutineScope interface with isActive and context properties;
  standard coroutine builders include it as receiver for convenience.
• Introduced Executor.toCoroutineDispatcher() extension.
• Delay scheduler thread is not daemon anymore, but times out automatically.
• Debugging facilities in newCoroutineContext can be explicitly disabled with -Dkotlinx.coroutines.debug=off.
• xxx-test files are renamed to xxx-example for clarity.
• Fixed NPE in Job implementation when starting coroutine with already cancelled parent job.
• Support cancellation in kotlinx-coroutines-nio module