python3: version neutral API

Using the six library we make version neutral API calls to
dictionary methods and to unicode methods.

partial: https://github.com/vmware/pyvmomi/issues/55
python3: replace thread module with threading

partial: https://github.com/vmware/pyvmomi/issues/55
python3: change call to urlparse

partial: https://github.com/vmware/pyvmomi/issues/55
python3: fix some syntax errors

partial: https://github.com/vmware/pyvmomi/issues/55