Add minimum python version requirement to README.md
Add minimum python version requirement to README.md

As suggested and accepted in #49.

arameshkumar/base-nuxeo-drive,ssdi-drive/nuxeo-drive,arameshkumar/nuxeo-drive,arameshkumar/nuxeo-drive,arameshkumar/base-nuxeo-drive,arameshkumar/nuxeo-drive,ssdi-drive/nuxeo-drive,arameshkumar/nuxeo-drive,ssdi-drive/nuxeo-drive,arameshkumar/base-nuxeo-drive,arameshkumar/base-nuxeo-drive