Implement Data Retrieval

Like I said in the email:

1. It's kind of hackish; it takes an FBID and an access token. If you're trying to test it get your FBID from here: http://graph.facebook.com/SHORTNAME where shortname is your profile name (if you don't have one, going to your profile should show your FBID in the URL). Get an access token here (and be sure it gets read_mailbox privs): https://developers.facebook.com/tools/explorer/
2. Group chats are just ignored right now.
3. This takes a while to run. It also hit the API call limit on my personal inbox, but this is probably because I was testing it a lot and because I have a really large limit.
4. I'm using the requests and dateutil libraries, I've included a requirements.txt file to install them via pip and added env to the gitignore for anyone who wants to use a virtualenv to test.