Make server usable for public use

[adelq]

Right now, the API in use by the mobile apps living at api.pennlabs.org can technically be used by other projects, but there are some barriers to more widespread use.

• Rate limiting - this API still uses the university OpenData APIs, which have severe limits. This alone prevents publication of the API at the moment.
• CORS - API currently disallows access from other domains per the CORS default, but for use on the frontend, nonsensitive endpoints should be allowed access.
• Documentation - enough said 😄