Upgrade Play-Streams so tests pass with Reactive Streams 0.4.0-M2
Refactor Publishers to use a SubscriptionFactory
Update Akka HTTP backend to use Akka HTTP 0.9
Merge pull request #3570 from richdougherty/akka-http-0.9

Upgrade to Akka HTTP 0.9
Added more Http Headers & fixed ETag header
Merge pull request #3601 from mkurz/httpHeaderFixes

Added more Http Headers & fixed ETag header