Switch accesstoken and client oauth models to use properly formatted "created" columns, fixes #245
Add migration to switch oauth tables to unix timestamps
Revert "Switch accesstoken and client oauth models to use properly formatted "created" columns, fixes #245"

This reverts commit 4226ab55f4fe3afb322975b00a920f5567378e36.
Merge pull request #247 from shadowhand/issue-245-datetime-columns

Migrate oauth tables to unix timestamps, fixes #245