Removed unused waitForKey() method from PlayRun

The method was copied to the PlayInteractionMode object in an earlier
commit. It should have been removed at that time, but must have been
forgotten.
Shut down Play threads in dev mode to prevent memory leaks

* Introduce ClosableLazy class. Like Scala's lazy, but allows
  closing of an initializaed value too.
* Made Execution.internalContext and Invoker.system into
  ClosableLazy values and close them on Server.stop().
* Also made AkkaPlugin's system a ClosableLazy. It was already
  being closed, but it used its own ad-hoc closing system
  based on Scala's lazy.
Merge pull request #1711 from richdougherty/run-thread-leak

Shut down Play threads in dev mode to prevent memory leaks
Updated intro docs for Activator
Updated Java/ScalaTodoLists with build.sbt
Merge pull request #1727 from jroper/activator-docs

Updated intro docs for Activator
Update WS documentation to use the Action.async builder.
Merge pull request #1730 from sluukkonen/patch-2

Update WS documentation to use the Action.async builder.
Added copyright statements to every file
Merge pull request #1733 from jroper/copyright

Added copyright statements to every file
Fixed MIMA

Just applying the fixes that I did on the 2.2.x branch to master, so
when we fork 2.3.x, it will be easy to enable MIMA.
Upgrade to Scala 2.10.3-RC3 and check iteratee memory leak is fixed

Scala 2.10.3 inclues a fix that allows memory to be freed when chaining
Future.flatMap calls (SI-7336). Iteratees make extensive use of
Future.flatMap, so upgrading to Scala 2.10.3 allows us to avoid memory
leaks when using iteratees (#1084). Memory leaks can occur when
processing large amounts of data or when working with connections that
can remain open for a long time.
Merge pull request #1735 from richdougherty/scala-upgrade-leak-fix

Upgrade to Scala 2.10.3-RC3 and check iteratee memory leak is fixed
Update email validation regex
Merge pull request #1738 from gmethvin/email

Update email validation regex
Updated contributor guidelines