Add DDT debugger

Summary: [[https://github.com/deviantART/ddt/blob/master/README.md | DDT]] is awesome.

Test Plan: Try `ddt` in browser console.

Reviewers: rjmackay

Reviewed By: rjmackay

Subscribers: dkobia, seth

Maniphest Tasks: T172

Differential Revision: https://phabricator.ushahidi.com/D1