Add schema.org markup to the <head>.

@ebidel @tjsavage 

The primary change is to add schema.org markup to the index and individual pages, as described at https://developers.google.com/+/web/snippet/

A secondary change is to properly escape HTML entities that might be present in post title metadata, to ensure that the schema.org markup is valid (and that the HTML is valid overall).

Once this is merged/deployed, we should test using http://www.google.com/webmasters/tools/richsnippets to confirm that the metadata is being picked up.

(Pro tip: every blog should start off with an article whose title includes <>"& characters as a way of forcing you to fix any escaping issues right off the bat.)