Chicago issue smash

On my travels to (and from) the excellent [Windy City Rails](http://www.windycityrails.org) in Chicago a few weeks ago, I took the time to address a bunch of issues here is the CHANGELOG broken down;

* Fix plugin config issues with user input (#225 #223)
* Fix Linux FPS timing issues (#215)
* Fix hook enable/disable issue (#206)
* Fix Git GUI issues (#196 #168 #193 #188 #159 #133 #123 #119 #104 #83)
* Mention Boxen script in README (#208)
* Explain global Git hooks how-to in README (#212 #112)

Also made some minor improvments to Linux Capturer class (the `--debug` was failing there).  Hopefully (thanks to the suggestion by @florianbachmann in #196) all GUI client issues should be solved.  

A combination of 2 path problems seemed to be the main issue (both Ruby and ImageMagick need to be in the path!).  A previous fix for we applied (for Ruby) had been incorrect.  I have tested all GUI clients mentioned in the related issues and they now all work (and capture) fine for me.