Configure settings from UI instead of YAML file #14

For configuring things that change more frequently. We currently have a hackathon.yml config that provides more static information (hackathon name, logic, etc), however there also exist things that are more variable:

• Slack invite URL
• Carpool doc link
• Contact information (general, travel Add config for bus captain notes #53, sponsorship)
• Sponsorship PDF link
• More...

Adding a simple admin UI + easy to use Ruby interface would make this much more accessible to non-devs, possibly even for some of the hackathon.yml variables.