Build: Move the saucelabs to grunt and optimized the .travis.yml

Yeah, I was thinking the same. The only thing is that it would also say that on pull requests. Maybe we can revisit that when Travis fixes the `TRAVIS_SECURE_VARS` varible, then we can do

```coffeescript
->
if process.env.TRAVIS_SECURE_VARS is "true"
  if process.env.SAUCE_USERNAME isnt `undefined` and process.env.SAUCE_ACCESS_KEY isnt `undefined`
    grunt.task.run [
      "pre-mocha"
      "saucelabs-mocha"
    ]
  else
    grunt.log.warn "'SAUCE_USERNAME' or 'SAUCE_ACCESS_KEY' variables not found, please configure them in order to run this task"
```