Merge pull request #68 from changbl/working

Fix bug and code cleanup
Modularize switch connection

Create three classes: Topology, VmacManager and FlowManager.
Multi-tenancy can be toggled on/off.
Zookeeper toggle
Merge pull request #69 from powerist/working

Modularize switch connection
Zookeeper toggle

Allow the user to turn on/off zookeeper storage
Merge pull request #70 from powerist/working

Zookeeper toggle
Fix DHCP, code style, and config options