chore(travis): log used ports
chore(travis): report both build number and id to BS
chore(travis): define a launcher for IE11 (SauceLabs)
chore(travis): switch back to SauceLabs

I think we are pretty close to be able to use both.

The xhr-polling seems to be pretty stable, but I'm having problems with multiple SSH tunnels (on BS), so let's try to switch back to SL.