Perform es6 transformations before linting.

Summary:
I copied over the transformation script used in kake and the package
requirements used in webapp.

Test Plan:
`make linc` - didn't fail to run and caught a few lint errors that I had
in my changed code

Reviewers: csilvers, alpert

Reviewed By: alpert

Differential Revision: http://phabricator.khanacademy.org/D6846