modules/tetra: add hostservpolicy module

This is similar to Cod's vhost checking code but it instead scans
incoming vhost requests against a set of policies. These policies match
via lua patterns and are stored as yaml inside etcd.

    λ etcdctl get /tetra/store/vhostpolicy
    ---
    num: 2
    pc:
    - uuid: 1
      pattern: foo
      setter: xena
      date: 1414967299
      action: REJECT
    - uuid: 2
      pattern: bar
      setter: xena
      date: 1414967303
      action: REJECT

The command VHOSTPOLICY has a few subcommands:

    Tetra(tetra@yolo-swag.com)- VHOSTPOLICY subcommands:
    Tetra(tetra@yolo-swag.com)- LIST       - lists policies
    Tetra(tetra@yolo-swag.com)- ADD        - adds a vhost policy
    Tetra(tetra@yolo-swag.com)- INFO       - gets information on a specific policy
    Tetra(tetra@yolo-swag.com)- DELETE     - Deletes a policy
    Tetra(tetra@yolo-swag.com)- End of command list