first pass mockup of user models
add fields to users models based on clarifications
add 'status' to VolunteerDonorRequirement table to track status of donation
rename KLPUser to User
implement signup, signin and signout end-points, fixes #61, #62, #63
integrate rest_framework.authtoken - generate tokens for users on signup and return in JSON with signin / signup
add test view to test authentication that works with both session and token based auth
remove Developer subclass since Developers can use same tokens to authenticate and dont need additional fields
set default authentication classes to token and session