Changes for ST3

Here are changes for ST3. First draft. It kills the version for ST2, so please don't merge.

I didn't test it really well. It would be nice if you included a unit test ;-). 'jQuery' and 'ace' downloaded very well. '666' went wrong. I didn't figure out why. Maybe you can.

- Changed for python3 packages
- Added file decode
- Added specific urllib exception