Install instructions for os x

[cswank]

When I run 'go get' on my project that uses this project I get an error:

github.com/vaughan0/go-zmq

./poll.go:4:10: fatal error: 'zmq.h' file not found

include <zmq.h>

     ^                                                                                                                                                                           

1 error generated.

The operating system is on OS X Mavericks and I installed zeromq from source with configure, make, make install which installs to /usr/local/include and /usr/local/lib

Could you please add some installation instructions? I'm not sure how to get this working.

[kevinpostal]

brew install zeromq