Travis setup 3

Third time's a charm

I've tested this as far as I can without it running on the skulpt account. If everything is as it looks this will:

* compare tags
* upload the build to the dist repository and tag it with the same tag as the one from skulpt
* it will also upload the HEAD version to the dist repository
* and it will update the site with the build of the latest tag called skulpt-latest.tar.gz and skulpt-latest.zip