Seed data

-Added seed data for assignments and repos
FYI, the name for the repos should be in the format of 'user/repo'. For example, our capstone repo would be entered as: `cmckee-dev/DPL-Student-Portal-Capstone`

This requirement is because of how the github interaction matches up what cohort to add assignments to based on this name. Perhaps we should add placeholder text to that field on the repo form to show that it needs to be in that format?