Update to Akka Streams and Akka HTTP 1.0-M1

This updates Play to use the latest milestones. These milestones
are based on Reactive Streams 1.0.0.M1.
Merge pull request #3720 from richdougherty/akka-http-1.0-M1

Update to Akka Streams and Akka HTTP 1.0-M1