Gemfile: add redcarpet markdown gem
TextBlocks: add db migration, model and spec
TextBlocks: add controller, admin page, layout helper and markdown view
rake/seeds: generate textblocks

Add app/templates/text_blocks, and use rake receipt to generate text
blocks.
Remove pages controller, re-route /terms, /imprint and /about
Merge branch 'refs/heads/zonque-cms'