+ added translate3d to mixins.less

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

last minute addition of a simple fluid grid for our fluid examples; it needs work, so we're not documenting it now

Cleans up IE7 inline margins for buttons and adds them for sprites, also fixes button padding for large/small sizes

 - Lets us use rounded corners in IE9
 - Makes hover / active states work correctly in IE<=9

Only change for non-IE is that moving from hover -> not hovering
no longer animates (was a subtle blend) due to mismatch between the
bottom of the gradient and the background color.

Refactor: moves the primary button background to match the others.

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

revamp the mixins file to organize things a bit more, make placeholder text use a new variable instead of relying solely on @grayLight

docs updates, forms updated to include error states and more examples, remove text-shadow from gradientbar mixin to fix bug