Improve HTML Detection in History Support Middleware

Use built in ExpressJS methods for detecting HTML in the Accept header.
Merge pull request #1228 from jherdman/improve-html-detection-in-history-support

Improve HTML Detection in History Support Middleware
Remove extra test noise.

`runCommand` already prints the output, there is no reason to log it
again.
Merge pull request #1232 from rjackson/remove-extra-test-noise

Remove extra test noise.
Allow running tests in production.
Merge pull request #1230 from rjackson/use-environment-consistently

Allow testing of production assets.
Provide Ember CLI version to Project model.
Merge pull request #1239 from rjackson/provide-brocfile-with-ember-version

Provide Ember CLI version to Project model.
Merge remote-tracking branch 'upstream/master'

* upstream/master:
  Provide Ember CLI version to Project model.
  Allow running tests in production.
  Remove extra test noise.
  Improve HTML Detection in History Support Middleware