ENYO-2877: Added .travis.yml for automatic run of jshint on pull-requests submission.

Enyo-DCO-1.1-Signed-off-by: Yves Del Medico <yves.del-medico@hp.com>
ENYO-2877: Updated to latest are-generator with automatic execution of jshint on pull-request submission.

Enyo-DCO-1.1-Signed-off-by: Yves Del Medico <yves.del-medico@hp.com>
ENYO-2877: Updated CONTRIBUTE.md about automatic execution of jshint on pull-request submission.

Enyo-DCO-1.1-Signed-off-by: Yves Del Medico <yves.del-medico@hp.com>
Merge pull request #466 from enyojs/ENYO-2877

ENYO-2877: Added .travis.yml for automatic run of jshint on pull-request...
Merge remote-tracking branch 'origin/master' into ENYO-2771