Revert "Fix relative CSS paths for github"

This breaks more complicated addressing schemes e.g. categories

This reverts commit a82d61f37b8358f260de9c36e06a911942f79840.
Set a baseurl instead of relative paths

See https://github.com/andrewshell/baseurltest

To run locally set an empty baseurl:
jekyll serve -w --baseurl=""

Note once a CNAME is setup this can all be removed
Add an example categories page and sidebar links
Add some example categorised posts
Fix category post urls
Add some missing site.baseurl tags
Add more test posts to check pagination works
Merge pull request #1 from manics/gh-pages

Initial attempt at using categories