Upload build SNAPSHOTS as tgz and as directory to DOPA server

This pull request will extend Travis so that on every push into stratosphere/master, a `stratosphere-0-4-SNAPSHOT.tgz` will be uploaded into  http://dopa.dima.tu-berlin.de/bin/

This is helpful if users don't want to build the system on their own.

Travis builds the files anyways to we can just ssh them to that server.