serve js/timezone.js with 'application/javascript' mime type instead of default ('text/html')

Google Chrome seems to have tightened execution security and hence the timezone.js served as 'text/html' will not be executed.

To fix this, the content type is set explicitly.
Merge pull request #361 from madscoaducom/patch-1

serve js/timezone.js with 'application/javascript' mime type instead of ...