add availability check after sign in to make sure the current mod hasn't alerady been done by user
Merge branch 'flash-and-messging' of github.com:LiminalSoftware/Categorize into flash-and-messging

* 'flash-and-messging' of github.com:LiminalSoftware/Categorize:
  Create styles for notice, alert, warning, and error flash messages.