Require Maven 3.0.5+ to build Rat, but only require Maven 2.2.1+ to use Rat.
We need Maven 3 to get around the problem of "The projects in the reactor contain a cyclic reference" when the "rat" profile is activated.

git-svn-id: https://svn.apache.org/repos/asf/creadur/rat/trunk@1622081 13f79535-47bb-0310-9956-ffa450edef68