Use 2.2-SNAPSHOT version of Play sbt plugin.

In this branch we are testing Play 2.2-SNAPSHOT
so let's make sure that version of Play and sbt
plugin match.
Use git-apply instead of sed for patching source files.

After banging my head for an hour how to make sed work reliably on both
MacOS and Linux I decided that's far easier to just use git-apply and
apply regular patches. They are easier to read than regexps and they can
be easily embedded into bash script.

//cc @fernandoacorreia
Latest results with Play's incremental compiler bug fixed.

Uploading results of testing against a local build of Play that includes
*both* of those patches:

  * https://github.com/playframework/playframework/pull/2237
  * https://github.com/playframework/playframework/pull/2274

Now, we can clearly see that name hashing is never worse and in some
cases (like securesocial) it's a lot better than previous algorithm.

//cc @fernandoacorreia