buttons: added large, small; misc changes

style/buttons.less: reverted :hover state to original effect; lighten
overall background of each button for a more visual 'pop'

style/mixins.less: removed unecessary white space prepending
browser-specific code

style/reset.css: changed vertical-align from BASELINE to BOTTOM to
ensure buttons were all lined up. if issues arise, revert.

style/setup-variables.less: added variables for small and large button
font size, affects padding