Hi Martijn
Regarding committer rights: I would prefer Marc Hoffmann as an author and project lead to give an answer on this question. As IMO he has ultimate word in such decisions. However as I know - we don't have formal rules written somewhere. So far we were proposing to become committer based on size of contributions and internal discussions on a case by case basis.
From here IMO the best way to get in - is to solve some outstanding tasks and go thru process of review by existing committers till acceptance.
And you're right - PR 97 is a PR for one (among many) of such tasks, most awaited one. For this feature there are many unfinished PRs, which focus on particular cases, lack tests, examples, documentation. In past due to lack of free time I didn't succeeded in finishing of this work by addition of missing parts and so on (shame on me) and Marc doesn't work on integration with Maven. If you're willing to take the lead here, your help will be appreciated. We can even do a live discussion via Skype or Google Hangout.