show file on /log

[stevekrouse]

Easiest first step is simply to link to files changed in commit by pulling from the changes property of commits in _data/git-log.json. We could either link to the live version on the website currently or the version tied to a commit hash on github.

The gold standard would be a diff view, like what gihub has for commits but rendered, where we show the old version and the new version. A collapseable / expandable iframe to github (which would have to go through a proxy because of x-frame stuff) could be what we want.