added the multichannelio.py object to neo/io

This new object should implement the capability of reading *.mcd files (files generated with the recording system from multichannel systems company). It was developed with numpy 1.8.1, quantities 0.10.1, and the neuroshare headers (0.9) for python that can be found at pythonhosted.org/neuroshare.
A file to test this code can be found here: https://www.dropbox.com/s/0a3m4dhbvtwr387/wn25_a2_amp14_100.mcd
written by Andre Maia Chagas
Contact: andremaia.chagas@gmail.com