Documentation writing

I've started writing some of the documentation for Themekey and we keep getting off topic in another thread so figured I would start one here.

See here for current info
https://www.drupal.org/node/2145521

@mkalkbrenner
I'll update to use system:dummy = dummy as soon as I get chance to try it out. I didn't know it existed, hence the need for documentation.

Yes I've seen the help files, didn't have them enabled when I first installed themekey. They appear to be of an older version of themekey? Maybe its just the theme?
I'll look over them and add/update examples to add to the doc pages. Seems a good idea we keep things consistent.