Make ActiveRecord query calls compatible with AR4
Fix broken period calculation initialisation
Fix broken migration that cannot access config
Fix payed→payed column rename migration
Fix column cache being out-of-sync after migration
Fix missing doctype in main layout
Style the no customer/invoices/projects alerts the same way
Add Dockerfile for deployment on Debian Wheezy
Mention that Ruby 1.8 is no longer supported; Ruby 2.x is supported