Added retina and button mixins

Added retina mixin (line 230) to swap larger images on retina screens.

Added button mixin (line 243) to quickly add background button
gradients using only one base color.
added delay parameter to animate mixin

Added delay parameter to delay mixin (line 334)
Fixed issue with columns and animation mixin

Fixed default fill property value for columns mixin. Chnaged it from
'auto' to 'balance' which is the actualy default value (line 27).

Fixed animation delay issue where there was an unnecessary '$' in the
variable.
Updated Read Me

Updated Read Me file to start documentation
Updated logs
Merge branch 'master' of https://github.com/chriscooley/Framework

Conflicts:
	compass_app_log.txt
	sass/_mixins.scss
	stylesheets/master.css