Icon consistency

As per #359, this standardizes use of icons.
- always use font-awesome: shouldn't even load glyphicons...
- remove `&nbsp;`s, use `fa-fw` to ensure spacing
- put icons inside links if they are next to a link
- in tree, "view on github" change to icon, like on notebooks
- in table, in addition to fixing a minor template, move the icons to the notebook links to break up space... not totally committed to this, but it does help break up the stream of text which is actually separate links.

the test fail is somewhat strange: can't reproduce.

there are probably a few other stylistic choices that could be made to tighten the overall feel
- the `rewind` for `up directory` is somewhat non-standard...
- back to top of page icon...
- eventual `/format/` icons...