[#73271234] Style apple touch icons

![screen shot 2014-07-28 at 11 13 37 am](https://cloud.githubusercontent.com/assets/228359/3715981/d16f91ee-15fc-11e4-8b17-af53f50f4abc.png)

that's small thing.. official bootstrap repo's mixin css file name is ```_mixins.scss```. 
would be nice to be same file name..? :bee: 
https://github.com/twbs/bootstrap-sass/blob/master/assets/stylesheets/bootstrap/_mixins.scss