Bug 937431 - [Tooling] make jshint a requirement on pre-commit r=rik

* changes how `make lint` works
* introduces a jshint-blacklisted reporter
* changes the pre-commit hook to run both jshint and gjslint
* changes the linters Travis jobs
* remove all predefined globals from the main .jshintrc default global
* add new jshintrc files for subdirectories
* add a README file in build/jshint/