created basic user model and migrated up
added basic tests for user model
added validations for presence of name and email, with corresponding tests
added validation and tests for valid email address format
added uniqueness constraint to user emails both at the model level and db level
added downcase_email on users before save
added bcrpyt gem
added password digest column to users table (with appropiate test)
wrote a lot of test for users password
wrote methods to make test suite pass for users passwords