Updates for BlueMix, show versions, etc.

Added manifest.yml to simplify deployment and support BlueMix.  Also uses a buildpack that supports Python 3.

Modified hello.py to show the version of Python and Flask and `run(debug=True)` if run locally.

Modified runtime.text to upgrade Python to 2.7.6

Modified README.md to mention BlueMix, add `git clone` and `cd hello-python`, simplifies cf push command, and add runtimes options.