Merge pull request #717 from sappo/master

Problem: No consistent code formatting.
Fixed Makefile for zpubsub protobuf example to use czmq_labs library.
Added some .gitignores for labs directory.
Merge pull request #718 from lovmoen/master

zpubsub protobuf example is not built using czmq_labs library.
Problem: New contributer don't know about best practices and automatic code
formatting.

Solution: Update the CONTRIBUTION.md to let them know.