Project score tweak

Initially the popularity scorer from https://github.com/24pullrequests/24pullrequests/pull/705 checked to see how many commits had been made on a project but the [commits api](https://developer.github.com/v3/repos/commits/#list-commits-on-a-repository) makes this call really slow when the repo has had a lot of commits in the last 3 months, it doesn't look like that endpoint respects any of the pagination options so there's no way to limit the response.

For now I'm just going to check to see if the repo has been updated in the last 3 months, which likely means there was at least one commit to master.

cc @kdaigle