Add eslint config and update repo to satisfy it

[picklechips]

This PR probably could have been separated up a bit but it does a few things:

1. Uses babel to enable es6 syntax
   • This involves some changes to the command to start the server, so i made nodemon a dev dependency and npm start now just uses nodemon by default
2. Introduces eslint (including into CI)
3. Updates repo to satisfy eslint rules

The eslint rules are based on airbnb-base, with the following rules disabled because they would require too many code changes for this PR (or I felt were unnecessary).

no-underscore-dangle
no-shadow
no-param-reassign
no-plusplus
no-console
no-restricted-syntax
no-await-in-loop
func-names