Multi Cluster Support

[thrawn01]

Purpose

To support replication to multiple clusters which may or may not be in different az or regions.

There have been several attempts

• https://github.com/mailgun/gubernator/pull/119
• https://github.com/mailgun/gubernator/pull/107
• https://github.com/mailgun/gubernator/issues/17
• https://github.com/mailgun/gubernator/pull/48

4th time is the charm... right?