Puppet Support

I was able to create a distributor without the required field 'distributor_config'. The documentation says it's required because it's not optional. I expect it is required because when you publish a distributor whose config is None you'll probably get an exception, so by not requiring it the user can get into a bad state.

To reproduce I did the following:
1. Create a repo named zoo-puppet
2. use httpie to create the distributor without its config by running the following:

http --json --verify no --auth admin:admin POST https://localhost/pulp/api/v2/repositories/zoo-puppet/distributors/ distributor_type_id=puppet_install_distributor

3. Now observe its output:

HTTP/1.1 201 CREATED
Connection: Keep-Alive
Content-Length: 405
Content-Type: application/json; charset=utf-8
Date: Fri, 04 Sep 2015 19:30:39 GMT
Keep-Alive: timeout=5, max=100
Location: https://localhost/pulp/api/v2/repositories/zoo-puppet/distributors/27484a4e-afd7-4cbd-ace0-fa18979ab406/
Server: Apache/2.4.16 (Fedora) OpenSSL/1.0.1k-fips PHP/5.6.12 mod_wsgi/4.4.8 Python/2.7.10

{
    "_href": "/pulp/api/v2/repositories/zoo-puppet/distributors/27484a4e-afd7-4cbd-ace0-fa18979ab406/", 
    "_id": {
        "$oid": "55e9f160549034239f55e877"
    }, 
    "_ns": "repo_distributors", 
    "auto_publish": false, 
    "config": null, 
    "distributor_type_id": "puppet_install_distributor", 
    "id": "27484a4e-afd7-4cbd-ace0-fa18979ab406", 
    "last_publish": null, 
    "repo_id": "zoo-puppet", 
    "scheduled_publishes": [], 
    "scratchpad": null
}

4. Notice the "config: null" part which will likely cause problems at publish time.

I expected a 400 response, but instead I received a 201.