Better bash highlights

I noticed that the asset URLs referenced `site.url`. In accordance with [Jekyll's suggestions](http://jekyllrb.com/docs/github-pages/) I changed that to `site.baseurl`. That just means that when you're running it locally you can 

    jekyll serve --baseurl ''

... and static assets will get referenced right. If you had another way you were handling this, let me know. In the meantime, the .css file makes the code look a little nicer, and I also added some more comments. Correct me if I'm wrong but I think `pycsw-admin.py` will be in the `sbin` directory.

Working on #191