De-dupe and update .mailmap

In the wake of https://community.rapid7.com/community/metasploit/blog/2013/12/31/metasploit-closes-out-2013 I noticed several dupes and failures to note Rapid7 accounts.

This should cover most of the contributors that have multiple `user.name` and `user.email` aliases in their various `.gitconfig` files, so we can correctly score commit counts. 

Like lines of code and hours spent, commit counts are a rock solid way of telling who's productive and who should be fired.