ML2 README needs updates for havana release

[Robert Kukura]

The neutron/plugins/ml2/README file contains statements such as:

  * Support for mechanism drivers is currently a work-in-progress in pre-release Havana versions...

  * Note that the ml2 plugin is new and should be conidered experimental at this point. It is undergoing rapid development, so driver APIs and other details are likely to change during the havana development cycle.

  * The following MechanismDrivers are actively under development for the Havana release:

that are clearly out of date. Also, a reference to https://wiki.openstack.org/wiki/Neutron/ML2 would be helpful.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/49978

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/49978
Committed: http://github.com/openstack/neutron/commit/2d7e2756271fff6413a572e11f9248465f23f1bb
Submitter: Jenkins
Branch: master

commit 2d7e2756271fff6413a572e11f9248465f23f1bb
Author: Bob Kukura <email address hidden>
Date: Sun Oct 6 21:41:08 2013 -0400

    Update ML2 README file for havana

    Closes-Bug: 1235308
    Change-Id: I684581c00ff28bc9cdb36034a9a970275b0a0090

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: milestone-proposed
Review: https://review.openstack.org/50391

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/50391
Committed: http://github.com/openstack/neutron/commit/15d863acf3ef15ad1fa63fe136c4c7b804705d36
Submitter: Jenkins
Branch: milestone-proposed

commit 15d863acf3ef15ad1fa63fe136c4c7b804705d36
Author: Bob Kukura <email address hidden>
Date: Sun Oct 6 21:41:08 2013 -0400

    Update ML2 README file for havana

    Closes-Bug: 1235308
    Change-Id: I684581c00ff28bc9cdb36034a9a970275b0a0090
    (cherry picked from commit 2d7e2756271fff6413a572e11f9248465f23f1bb)