Scrape new Vundle-managed plugins from dotfiles repos

Summary: Resolves #35.

Test Plan:
Changed code so that we'd only search for
https://github.com/search?q=dotfiles+user%3Ablakewilliams&type=Repositories&ref=searchresults

Ran `PYTHONPATH=. python tools/scrape/scrape.py -s github-dotfiles 1`, ensured
no plugins were found. Made this change, ran that command again, saw that 32
Vundle plugins were found.

Reviewers: xymostech, spicyj

Reviewed By: spicyj

Differential Revision: http://phabricator.benalpert.com/D207