Add matoi/config.
check `db` presence due to spec/spec_helper.rb's groonga::database hack
fails.
circular_array_spec: set groonga to be false because it doesn't require
Add sewell as dependency
Fix groonga schema to be suitable

* Add profile_image_url* on users table
* Add url on urls table
* hour and day columns on tweets table are now unsigned_integer16
* hours and days tables are removed
Add lib/matoi/tweet.rb