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

move around some comments in buttons.less, update labels to use correct variables, add snippet to docs about IE9

 - 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

rewrite alert messages to use less code, combine the look of default and block messages, simplify docs

move mega link footer to scaffolding to try it out, fix broken button text shadow, change UL/OL margins back, make li color same as body

breaking out patterns.less even more, removing unnecessary div from checkbox and radio lists--now just labels and inputs