Updated the dependency of CodeNarc to v0.22

Since CodeNarc v0.22 introduced a bunch of new checks which I'd
like to use in grails-projects as well I've upgraded the dependency
to the current CodeNarc version. Compilation with Grails 2.1.2
was successful as well as the execution of the contained tests.
Merge pull request #4 from schoeffm/upgrade-to-codenarc-0.22

Updated the dependency of CodeNarc to v0.22