Improve sdist and bdist packaging

* Include tests in sdist
* Include license and notices in all distributions
* Update manifest
* Use more conventional file names for licenses, notices, etc.

related to https://github.com/vmware/pyvmomi/issues/133
related to https://github.com/vmware/pyvmomi/issues/123

closes: https://github.com/vmware/pyvmomi/issues/139
tox support

initial tox support

addresses: https://github.com/vmware/pyvmomi/issues/131
closes: https://github.com/vmware/pyvmomi/issues/136