Update migrations for rails 4

update_all changed between Rails 2 and 4. It's no longer an ActiveRecord::Base
method; it now lives in ActiveRecord::Relation. Previously, the update_all method
allowed you to supply selection parameters  (e.g. WHERE should_update = true)
along with new values for certain columns. Now, you run a Model.where method,
then call update_all on the resulting ActiveRecord::Relation.

Don't think this will have any side effects, since all of these migrations have
already been run in the important places. Note that db/structure.sql has
changed, though.
Merge pull request #465 from sunlightlabs/migrations

Update migrations for rails 4