Allow for modularization of this library

I renamed the "nx-os" folder to "nxos" so that it can be referenced in an import statement. Forgot to mention this in my previously opened issue, so just wanted to make sure it was clear. This was out of necessity....hyphens cannot be used in import statements.

This was the major change - I also made some enhancements to the example script I created, as well as update the README with some basic instructions for how to build this python module.