Remove numpy use from pymatbridge.py.
Merge pull request #76 from isbadawi/less-np

Remove numpy use from pymatbridge.py.
Rename json functions away from +pkg syntax.
Use Octave-compatible syntax for calling Java.
Add support for invoking Octave instead of Matlab.

* Extract most of the Matlab class into a base Session class
* Matlab and Octave are subclasses that tweak the command line
  invocation
* Eliminate some code duplication along the way