Convert to Hakyll

- Add cabal file and LICENSE
- Convert Jekyll templates to Hakyll templates
- Remove unneeded Jekyll content
- Replace bin/ with a Makefile
- Move _posts to posts
- Render my own feed to retain existing content
- Change post metadata:
  - Layout is not supported
  - Title should not be quoted
  - Tags need to be comma separated
Move indexRoute and indexedUrlField upstream
Implement next/previous links