After migrating to eslint some errors were disabled to make it easier to
migrate.
This enables all the lint rules and treats all warnings as a build
failure. Similarly, CI won't automatically try to fix mistakes.
Change-Id: I80f808af026fc51bed90421b3b24737994a52094
tslint has been deprecated so it's nice to switch to eslint.
Currently this uses a minimal eslint, to get things up and running.
node-sass requires C which does not work nicely on all platforms.
Change-Id: I3ca9adf2971475c009e541652b7637c18ad960f4
