compute and display karma

I've heard of sites that give you more karma for "posts" than
"comments" by, like, an order of magnitude, which I think is way too
extreme. But, like, a little less than half an order of magnitude
sounds about right.
more attractive comment rendering, comment form

Also, some code style adjustments.
Merge pull request #3 from zackmdavis/an_impulsive_branch

karma, comment rendering improvements