Frank doesn't work with tmux

[x1024]

I had this exact issue today:
ios-control/ios-sim#21

Removing tmux fixed the problem, but it took me more than an hour to find this issue (i had to go through frank, then sim_launcher, then finally ios-sim to get to it).

I suggest that a "Toubleshooting" section be added to the README, addressing this issue.

[moredip]

Can you add an entry to the README, or even better to the website's FAQ page: https://github.com/TestingWithFrank/testingwithfrank.github.com/blob/master/faq.md