Removes bettertouchtool

- We don't think this is a heavily used utility
- it wasn't able to download
- which meant we couldn't build a developer image

==> Downloading http://www.boastr.de/BetterTouchTool.zip
curl: (7) Failed connect to www.boastr.de:80; Connection refused
Merge pull request #41 from codeword/drops_btt

Removes bettertouchtool