bake: Use standard pickle and queue for now to fix some small issues. * JSON leads to some problems with integers as keys. * Add some stats to the baking process.

cov-core==1.15.0
coverage==4.0.3
invoke==0.12.2
mock==1.0.1
pytest==2.8.7
pytest-cov==2.2.1
pytest-mock==0.10.1