Style improvements

Done along with @mollymcleod!
I'm fond of using a general-to-specific naming convention so Sublime Text and other editors can suggest different autocomplete options as part of code hinting. $green-dark, $green-medium, $green-light, etc. (An example of more thinking on this: http://webdesign.tutsplus.com/articles/quick-tip-name-your-sass-variables-modularly--webdesign-13364) How does that sound to you two?