Update README.md - note on versions 
Update README.md - note on versions 

Update to point casual users to pypi and pip installs.
serialdoom/pyvmomi,michaelrice/pyvmomi,chenpiao/pyvmomi,tianhao64/pyvmomi,hartsock/pyvmomi,virtdevninja/pyvmomi-ce,vmware/pyvmomi,Infinidat/pyvmomi,davidmontgom/pyvmomi,alexkolar/pyvmomi,spicykaiju/pyvmomi,gdowding/pyvmomi,borland667/pyvmomi,higebu/pyvmomi,rhadman/pyvmomi,y12uc231/pyvmomi