Sort candidate's candidacies in date order. Fix #7

This needs to be written as an SQL query as there's no way I can see in
DataMapper to order a result set by a column in a joined table (the
election date).
Make Date.parse work
Revert "Make Date.parse work"

This reverts commit e8b5147b6c05f0a003631983a30b149c08b24775.
Revert "Revert "Make Date.parse work""

This reverts commit 445994f962929b9009d7b4663fcaf99b852159c1.
Revert "Revert "Revert "Make Date.parse work"""

This reverts commit 864478f2a581420826d28a7ae3ea6d8a42583337.
Add Gemfile
Delete .gems
Use ruby 1.9.2 for compatibility with Heroku bamboo stack
Remove ruby declaration as Heroku bamboo ignores it anyway (and uses bundler 1.0.7)
Remove pat gem
Fix date parsing (it should be a Time not Date object)
Fix Postgres/sqlite type error by using Postgres, closes #7