use tabs not spaces

This is a living document to serve as a go to style guide for javascript at Pardot.
We forked this from airbnb so at the moment, it will not match our current codebase.

Since our existing styleguide is currently unwritten, please don't push directly to master. Use a PR so we can have a community consensus.

This first PR changes the styleguide to use tabs and not spaces for whitespace.

@slawder - you may want to open up the permissions for the pardot/javascript repository to our entire organization so we don't have to create our own fork to make PRs.

cc @mbaxter-pardot, @bgrimes, @znbailey