Syntax check rake files

I added the ability to specify multiple file types for an overcommit
check, and made it check ruby style and syntax on rake files as well.

Change-Id: Ib737af6c9d9a8fd3b66c2ce0558e1bb51f3a7d85
Reviewed-on: https://gerrit.causes.com/25541
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>