file removed from gmusicapi
first crack at doing our own oauth (instead of relying on gmusicapi) and accessing email address (to support separate accounts for users).  oauth flow is working, just needs some cleaning up
change constants to a (somewhat) cleaner "enum" style
some more refactoring for config file locations.  get rid of global config variable, make read_config and write_config more generic
add beaker for session management.  store user oauth info in user directory
add exception handling around read_config if config file doesn't exist
add a helper for getting the session
make configured watch paths to be set per user
abstract user info out into user class, make file_watcher a class, move some helpers into a separate util file
display email of logged-in user
first shot at supporting multiple accounts.  looks to be working fairly well in my (basic) tests
use refresh token if a user is already logged in so we don't need to prompt ever time
don't override 'uploaded' status when re-scanning