Factory tests

I populated the context for Student, and wrote as many factory tests as I could come up with. I have a few comments that I wrote in the code with questions for how we should go about things. I also incorporated some of my thoughts here:

1) I believe that all of Pittsburgh is considered Allegheny County so will any of the "school_county"s be different?
2) We need a way to distinguish between students who have allergies and who don't (i.e. some standardized entry for students without allergies; "none" is a possibility). And the same for medications.
3) I think the 'team_id' field should be moved from the Registration model to the Student model because we don't know what team a student is on once they register. A second option would be to add a separate associative entity like "team_history" or "team_registration".