Clean up old remnants

[amontalenti]

• [x] No need for the flowdock icon any longer
• [x] My .hgrc is no longer necessary; may want to scan other old dotfiles, too
• [x] README doesn't need to mention Mercurial
• [x] Given my frequent use of pyenv, requirements.txt is probably no longer necessary
• [x] No longer using quicktile
• [x] Doubtful that this Google Talk hack is still working
• [x] Not sure this .desktop file for Sound Settings still works
• [ ] Haven't used tmuxp in awhile
• [ ] Not sure that .Xmodmap is still actually working
• [ ] My fabfile.py has some cruft that could benefit from cleanup, such as some @hosts directives, etc.
• [ ] The odd ~/opt/bin script might need an upgrade from Python 2, or a replacement/delete, depending