Preliminary attempt at brewing rtags.

This doesn't work right now for several reasons:

- 1.0 release (a while ago) doesn't seem to work at all for me
   - could be the tar is missing things
   - could be that the process was different back then
- HEAD release does come close ('brew install rtags --HEAD')
- fails to complete since rtags has no install target
   - i.e., there is nothing to install
   - probably best to add it for everyone (install to prefix)

Some other general comments about the rtags programs:

- names (rdm and rc) are a bit confusing
   - (wasn't rc the original shell for Unix?)
      - http://en.wikipedia.org/wiki/Rc
   - how about something like rtagsd / rtags or rtagsd / rtagsc?
      - it's your program, name it what you want, but it may conflict with some things