Add counts to models

Because DRY
Rename certificate dump methods
Genericise upload method
Put directory into a method for reuse
Require CSV class
First pass at stats generation
Add counts of certificate levels
Forgot to rename methods in tests
Only get published certificates per level
Typo with rake tasks
More naming changes

Naming things is hard
Tests for statistics
Remove rake tasks
Refactor dump methods for use in delayed_job
Add migration to set up delayed job
Bump alternate-rails version
Add csv format to `/status`
Link to CSV dump on `/status` page
Typo
Get statistics via Fog, rather than the HTTP url