wrote rake task cg:upgrade:init_created_at to set created_at for all Membership / Tagging / Task / Profile records
task cg:upgrade:init_created_at: use update_all instead of iterating over all records
Merge pull request #48 from Crabgrass/bugfix/4281-rake-task-to-add-created_at-where-needed

wrote rake task cg:upgrade:init_created_at