Warn and exit when running inside tmux on OS X

tmux loses access to its original namespace on OS X which causes Chrome to
crash. See
https://github.com/ChrisJohnsen/tmux-MacOSX-pasteboard#interaction-with-tmux
and http://savanne.be/804-running-karma-and-chrome-under-tmux-on-osx
Merge pull request #31 from martinp/tmux-warning

Warn and exit when running inside tmux on OS X
update README to fix #30
Merge pull request #32 from TomTasche/patch-1

update README to fix #30
Change to stable GoogleMusic endpoint
Removed twisted
PEP8 fixes
Merge pull request #40 from dz0ny/without_twisted

Without twisted
Fix multiline
Release 0.0.2
Update README.md
Merge branch 'master' of https://github.com/dz0ny/leapcast

Conflicts:
	leapcast/__main__.py