Add more color to elements

[bitprophet]

Note: not make more colors configurable, but make some elements that are currently transparent or black and white, colored (though these would of course be configurable too).

Cribbed from #6 and #28:

It also made me realize that it'd be nice to just have a bit more color in the theme overall. Not so much as to undermine its low-key feel, but enough that one can make an Alabaster site look different from the default w/o resorting to custom stylesheets.

Add more colored elements overall, e.g. perhaps make some thick top or bottom borders on headers or on the sidebar or something. Some common visual elements that stand out a bit and can help tell Alabaster-using sites apart with a single color change.

[kennethreitz]

:-1: