Merge branch 'es6-specs-pls' into 'master'

Add es6 to teaspoon

## What does this MR do?

Adds the `es6` file extensions to teaspoon matchers so it can load those specs.

This also removes the current coffee matchers.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

We need to accept `.js.es6` specs.

## What are the relevant issue numbers?

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5524

spec/teaspoon_env.rb

@@ -38,7 +38,7 @@ Teaspoon.configure do |config|
 
     # Specify a file matcher as a regular expression and all matching files will be loaded when the suite is run. These
     # files need to be within an asset path. You can add asset paths using the `config.asset_paths`.
-    suite.matcher = "{spec/javascripts,app/assets}/**/*_spec.{js,js.coffee,coffee}"
+    suite.matcher = "{spec/javascripts,app/assets}/**/*_spec.{js,js.es6,es6}"
 
     # Load additional JS files, but requiring them in your spec helper is the preferred way to do this.
     # suite.javascripts = []