Improve error handling

[jeremyd2019]

Right now, basically no errors are caught, leaving them to be caught by flask. When debug is turned off (which it should be in production), a generic 500 error page will be returned, and the stack trace will go to a server log somewhere.

This project was mostly a proof-of-concept from my standpoint. I am no web developer and was not pretending to be, I just picked a python web framework pretty arbitrarily, grabbed some tutorial code for it, and grafted the github api calls I was actually interested in onto it. As such, this is missing all of the spit-and-polish that a real live web app ought to have, like proper error handling and reporting.