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

change up the z-indexing and add some popover/twipsy content to the test modal on the js docs to help avoid future bugs

another quick pass at ranking all zindexes and listing them in variables for quick overview and editing later

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

fix uber size in responsive; remove @extraspace variable by changing grid to use :first-child over negative margin

update variables to inlude @baseFontSize, @baseFontFamily, @baseLineHeight for easier customization; added placeholder for @primaryButtonColor, but didn't implement

huge update to forms, docs for the new forms, added a new link for js example to tabs/pills, add some new mixins

remove theme.less and split preboot.less to mixins.less and variables.less to isolate customization from function