Support Play 2.3.7 instead of Play 2.3.5

I added a commit to Play for @breskeby so that it no longer says you're running SBT when you're really starting it from Gradle :-)

https://github.com/playframework/playframework/commit/01a73b24652e5c181948fb6e538ad0f00a773636
https://github.com/gradle/gradle/commit/1de14e43728bde17ffef466fb148e3440b951564#commitcomment-8764498

I'm not sure how to test out the Play support to see if there's anything else I could do for you guys. Is there a way I can build Gradle from source and use that version instead of the version I currently have on my path? Or will there be a version of Gradle released soon that will have some of the Play support stuff in it?