Change standup.app to standup.main; pep-8 cleanup

There are too many things named "app" so this changes the standup.app
module to "standup.main" which isn't a great name, but better than
having multiple app things.

This also does a code cleanup pass fixing end-of-line things,
organization of imports, ...
Use in-memory db for testing; and pep-8 fixes
Add comment of vital importance

This bumps me up another shade of green! Yay!
Change self.app to self.client

One more thing named app down!
Update migration documentation