Removed CZMQ as a submodule
Squashed 'czmq/' content from commit ca91178

git-subtree-dir: czmq
git-subtree-split: ca911787c3ae6a08855841bbbf4f6e024423a0dd
Merge commit '0971b62db8000d5e4557541d7e73a86ff2cfec88' as 'czmq'
Updated README with instructions about git-subtree