documentation Updated README.md for module release

Updated the README.md documentation in anticipation
of the puppet-quantum 2.0 release (Grizzly). Matched
style to other modules, added a short example, and
included links to further documentation and resources.

* Added example code to enable quantum networking in nova.
* Included a list of other quantum network drivers of
interest.
* Updated contributors to point to the latest github
graph.
* Trailing whitespace removed.
* Added cisco-quantum to documentation
* backticks around inline source

Change-Id: Ice968a719541c8e3a8924647690a99ef6d304378
Merge "documentation Updated README.md for module release"
Add support for provider networks

Quantum lost the ability to configure provider
networks between folsom and grizzly in part
due to changes made in commit 094c2ae:
only set network_vlan_ranges for vlan network types

Since network_vlan_ranges informs the plugin
which provider networks are available, it is
still needed even when not in vlan mode.

This patch changes the behavior to be:

- if the user sets vlan_ranges, the config option
will be set regardless of plugin

- if the user doesn't set it, a default is used
when in vlan mode, while the value is ensured
absent when in gre mode.

Change-Id: I1638d28da87041798c0b183923137c3bd535c6c3