[cmeacham98]

Only count pull requests that are merged. Make this fact obvious on the hacktoberfest website so contributors know spamming PRs will not help them.

I know the standard answer to this is that it would exclude some repos (ex: node) that merge PRs manually via git. However:

1. You already are excluding every open source project not on GitHub, so this is a really weak point.

2. I am extremely confident trading off not including a very small subset of repos for removing the incentive to spam bad PRs is a worthwhile trade.