Add template tags to display posts

This completes section "Adding the template tags" in the webdesign
guide. You can see the post now yay!
Add note about date formats in readme
Add markup to index.hbs

Finishes up to step 9 in "Adding Markup" section.
Add notes about wai-aria and schema.org
Add markup and tags to post.hbs

This finishes up to step 3 in "Writing the post.hbs file" section.
Add more notes to readme about post.hbs