Overhaul JS linting/testing

Currently, we are using jshint/jscsrc to provide linting for all our js. However, this is not enough and is also not supported anymore.

1. jscsrc has been merged into eslint and is no longer supported/updated outside of eslint.
2. It only provides in editor hint/lint capabilities for those who understand how to use it.
3. Lastly its very limited and does not follow current best practices

I propose replacing it with some form of eslint or equivalent to allow for far more possibilities. I also would like to setup and establish tests to enforce the new standard. This will also require some overhaul of our current js. Its main use will be for controlling the JS for the new theme however

Specifically, I would like to use https://github.com/sindresorhus/xo which is a simplified wrapper for an eslint standard config based on the Javascript Standard Style with the proper changes for most normal JS programmers and the ability to modify the config.