Added the ability to associate both nonprofits and sponsors to a challenge. Cleaned up some views.
Add the ability to remove nonprofits and sponsors from a challenge.
Fix issue related to adding sponsors.
Fix devise implementation.
Complete login/logout functionality.
Added the ability to add new users. Only authenticated users can perform crud operations.
Add ability to Admin to change their own password.
Prevents removing admin if no other admin is remaining. Added admin creation to db:seed.
Fixed issue related to Challenges_teammates dependency preventing Challenge from being deleted. Replaced that relationship with a join model that better reflects the relationship between Users and Challenges.
Merge branch 'milestone2'