overhaul grid mixins and variables, standardize fluid grid system and enable it across responsive layouts

change text on js docs page to improve rendering on iphone, update responsive for carousel considerations

overhaul frontpage jumbotron, add js for twitter buttons back in, fix up some form ids and classes, straighten out the use of primary button variable

update docs to include separate responsive css, update docs to highlight proper file name, updated makefile to build responsive separately

move css builder and downloader to dedicated page, start to update remaining sections on LESS docs page

adding actual images to carousel to ensure you can see things are animating; updated styles of carousel controls to work on light and dark backgrounds and use opacity for effects

docs updates to make the getting started section more responsive, updated the benefits to be clearer and swap x for checkmark