fix-failing-travis: Update .travis.yml to facilitate the `canvas` package.
fix-failing-travis: Update .travis.yml to facilitate the `canvas` package.

- Add '--build-from-source' install instructions.
- Include addons/env for canvas cairo, etc dependencies as node-canvas does: https://github.com/Automattic/node-canvas/blob/master/.travis.yml.

ihmeuw/beaut,ihmeuw/beaut,ihmeuw/ihme-ui,ihmeuw/beaut,ihmeuw/ihme-ui,ihmeuw/ihme-ui