Compile spike sort on OS X

Added Xcode options sufficient to make this compile if Google Protocol
Buffers (protobuf-cpp) and 0MQ (zmq) are installed via MacPorts.

A nice person could add similar search path options to handle the
homebrew case.
Merge pull request #155 from awidge/spikesorting

Compile spike sort on OS X
Merge pull request #3 from open-ephys/spikesorting

Spikesorting update