Send close control frame on client-initiated disconnects
Merge pull request #2458 from andrewconner/ws_close

Send close control frame on client-initiated disconnects
Add headers methods to WS API
Merge pull request #2371 from gmethvin/headers

Add headers methods to WS API
Upgraded all dependencise of Play

* Didn't upgrade to hibernate-validator 5.1.0 because it adds a number
  of extra JEE dependencies that I'm not sure we want.
* async-http-client 1.8.x changed the package of cookies, the
  Cookie constructor, and the available properties.
    - Removed version property from Play cookies because AHC doesn't
      support it anymore
    - Added expires property to Play cookies because AHC does support
      it.
    - Made the Scala API return Option for maxAge and expires, returning
      None if the server doesn't set it, or Some if the server does.