dependency issue

[ukos-git]

Seems like protobuf-to-dict depends on six>=1.9.0 but in their repo's requirements it is only refered to six 1.8.0
An issue is already active at the developer's repo (#benhodgson/protobuf-to-dict#12) but the repo seems to be stale.
I recommend adding the six dependency to our requirements.txt (right before protobuf-to-dict) because it raised strange errors on debian8 having six 1.8.0 installed. updating six to 1.10.0 fixed the issue for me.