Clear session if an exception is raised in "save"
Update Save handling

Saves are now done in after_request callbacks so errors can be handled
cleanly.

clear() is always executed in the app context teardown.
Fix save calls again

This time we replace and wrap the full_dispatch_request so we can
trigger the save when the response is done, but also have exceptions
handled by Flask wsgi_app.

the AppContext pop is now just a clear.
Fix import error
Merge pull request #3 from chillinc/master

Merge save changes