Add UglifyJS installation to travis build.
Add UglifyJS installation to travis build.

Mogztter/opal,jgaskins/opal,kachick/opal,wied03/opal,jgaskins/opal,kachick/opal,Mogztter/opal,opal/opal,iliabylich/opal,Mogztter/opal,Mogztter/opal,opal/opal,kachick/opal,iliabylich/opal,opal/opal,kachick/opal,jgaskins/opal,iliabylich/opal,wied03/opal,wied03/opal,opal/opal