Correct name of players table to lower case; make username unique and relax unique constraint on first + last name
Correct reference to player_id by using standard `references` approach
Correct typo
Use standard `references` approach for vocab_questions.game_id; player_answer is an integer (word location index)
Remove vocab_ from model names; it is redundant since this is the vocab app :-)
Added model relationships
These two methods are questions you can ask about a Question object, so we make them instance methods on the Question class
Typo fix
Merge pull request #1 from qiuey00/nick/initial_models_fixes

Nick/initial models fixes