refactored sdk into a module named FuelSDK

This is a fairly major refactor, but supports the sample files exactly as they are.

Added a setup.py file for easier installation and registration at pypi.

Created a python module, FuelSDK, as the root. Before ET_Client was being used as the python module and the client class name. This was a little confusing.

Broke apart the classes into modules to better distinguish their roles. (i.e. client, objects, rest)

Added VirtualEnv folder to gitignore for sandbox development.