Add style checker for Javascript using Closure Linter
Refactor closure-lint provisioning

Bootstrap Pip in base, and use it to install closure-lint
Update Credits and README
[Fix #245] Merge branch 'yasuyk-javascript-gjslint'

* yasuyk-javascript-gjslint:
  Update Credits and README
  Refactor closure-lint provisioning
  Add style checker for Javascript using Closure Linter