Use colors from new Jekyll site

Thanks to mojombo/jekyll#583
Use relative URLs in inter-post links
Steal GitHub's syntax coloring
Reorganize syntax rules

No actual style changes
Suppress spurious errors
Tweak coloring
Fix indents
Add title hover
Fix min-height for sidebar
Don't shim newer IEs
Add missing seconds
Set permalink URLs for new posts
Relaunch! :trophy: