Fixes #158

* Refactored IPPolicy.get_ip_policy_rule_set to use IPRange instead of
  IPNetwork index splicing because they are not supported in netaddr
  for ipv6.

* Added unit test case for IPv6 subnet for
  IPPolicy.get_ip_policy_rule_set

* Modified an IPAM unit test to have correct parameters for test's
  original intent.
Merge pull request #163 from asadoughi/master

Fixes #158
LGTM
setup Travis CI to run test coverage

- Set the minimum test coverage number to 90%
- Get 100% test coverage on security groups and subnets
- Add more test coverage on networks
Merge pull request #162 from jmeridth/run_test_coverage_on_travis_ci

Setup Travis CI to run test coverage
Merge pull request #164 from Cerberus98/master

Ensure we're always trying to iterate over a list
Updates Mac Address port return format
Merge pull request #165 from Cerberus98/mac_address_fix

Updates Mac Address port return format
First cut of modular network plugins

Adds the network plugin concept to quark, as well as a new "bridge"
column to the port model for dual mode networking support. Also bumps
the test coverage back up to 90%.
Merge pull request #166 from Cerberus98/default_nets_merge

First cut of modular network plugins
Fixed tenant_id and device_id filtering.

Changes made after the network sharing busted tenant_id based filtering.
Also noticed that the model_query call was making an explicit filtering
choice on Ports for device_id, so that particular filter was moved into
the port_find method.