Update README.rst - link to tox project

A link to tox project documentation will make it easier for new developers to setup tox for the first time.
respect venv

Change shebang to use env to ask for the python interpreter,
this allows the scripts to run while respecting a virtual
environment.

Closes: https://github.com/vmware/pyvmomi/issues/151
Merge pull request #152 from hartsock/samples

respect venv
Fix a typo in README.rst
Merge pull request #154 from ivuk/fix-typo-readme

Fix a typo in README.rst
Update setup.cfg

Sets requirements for rpm packages.
Merge pull request #155 from FrankCRoth/patch-2

Update setup.cfg