Tweaks to gitignore

* adds `_site` and `_posts` to avoid shenanigans when switching from
  `gh-pages` branch
Remove unnecessary whitespace
Merge pull request #290 from duggiefresh/master

Remove unnecessary whitespace
Add ES6 Import Validation

- Add dependency broccoli-es6-import-validate
- Add validateJs tree (only when env !== 'production')
Merge pull request #285 from twokul/gitignore

Tweaks to gitignore
[fixes #302] although location auto requires server side support, I would like to push for it as the default and aim to provide the appropriate server side components to make it seamless.
document.location.origin is not needed, and fails in IE
Merge pull request #209 from jgable/es6ImportValidate

Add ES6 Import Validation