add linting using eslint consuming the rackt config

[pwmckenna]

while the style will probably change as more repos are updated (hence the overrides for this repo), this PR introduces eslint and uses the rackt eslint config). I didn't want this to change any code, so rules that did not pass were overridden/disabled to just enforce the style that already exists.

Here is the repo for the base config being enforced: https://github.com/rackt/eslint-config-rackt

The original discussion around a centralized eslint config can be found here: remix-run/history#112

[danez]

This is now not needed anymore after #100