[docs] How to contribute page at Mirantis site contains outdated info

[Mike Scherbakov]

http://software.mirantis.com/how-to-contribute/ page has references to Savanna, not Sahara.

Also, it has refs to https://sahara.readthedocs.org/en/latest/ , which responds to me with "This webpage has a redirect loop". Main launchpad page https://launchpad.net/sahara also has reference to broken readthedocs.

[Sergey Lukjanov (slukjanov)]

https://sahara.readthedocs.org/en/latest/ is working ok now