Temp bug fixes and past due interface

[ennukee]

As well as a new changelog bit. Here's what that says:

Changelog

1/30/2016 Update

• Bugfixes
  • Added a temporary log out button while I investigate Heroku bootstrap issues
  • Removed 'X' button on notifications, as Heroku breaks the bootstrap behind it
• Features
  • Added a new 'Past due' section to quickly monitor and remove past due assignments
  • 'Due within a week' assignnments (should) no longer include past-due assignments
  • You can now mass delete all past due assignments