Added 'xo' and formatted all files to comply with linting

[emhagman]

I went ahead and added the xo library. The linting is ran in the test script in package.json. I also added a command called autoformat that will do most of the heavy lifting for most people when trying to adhere to the style guidelines. There is a convenience method called lint as well. All of these can be run via npm run [name] like npm run lint.

I know #455 discusses this and believe this will close it out as long as everyone agrees this is the code formatting / linting tool we want to use.

If anything needs to change let me know!

[coveralls]

Coverage decreased (-0.7%) to 90.875% when pulling ebe7b52 on draftedus:xo-lint into d8e1da3 on agenda:master.

[emhagman]

I just saw #471, should I close this?

[coveralls]

Coverage decreased (-0.9%) to 90.689% when pulling ebe7b52 on draftedus:xo-lint into d8e1da3 on agenda:master.

[coveralls]

Coverage decreased (-0.9%) to 90.689% when pulling ebe7b52 on draftedus:xo-lint into d8e1da3 on agenda:master.

[OmgImAlexis]

Yep close. I'll redo this once more of the higher priority PRs get merged. Sorry for you adding this extra work. 😞