1.2.0

• Kotlin updated to 1.3.30.
• New API: CancellableContinuation.resume with onCancelling lambda (#1044) to consistently handle closeable resources.
• Play services task version updated to 16.0.1.
• ReceiveChannel.isEmpty is no longer deprecated

A lot of Flow improvements:

• Purity property is renamed to context preservation and became more restrictive.
• zip and combineLatest operators.
• Integration with RxJava2
• flatMap, merge and concatenate are replaced with flattenConcat, flattenMerge, flatMapConcat and flatMapMerge.
• Various documentation improvements and minor bug fixes.

Note that Flow is not leaving its preview status.