add rich snippet info, improve meta

* ref for rich snippet: http://support.google.com/webmasters/bin/answer.py\?hl\=en\&answer\=146646
* ref for meta: http://support.google.com/webmasters/bin/answer.py\?hl\=en\&answer\=35624\#1

Not putting a meta desc into post pages for now so that google just uses the post excerpt.