Add a test against py35
Restore PySide install for 3.5
Do not try and install simpleitk on py35
Fix syntax in optional requirements file
Allow simpleitk on python 3.4
Do not try simpleitk on py3.4
- Now using the latest pip
- imread wasn't actually being installed
- Optional package installation uses a requirements file
- `python setup.py develop` instead of the previous two-step.