Extend rax_clb module to configure SSL termination and HTTPS redirection.

Rackspace Cloud Load Balancers support [SSL termination](http://docs.rackspace.com/loadbalancers/api/v1.0/clb-devguide/content/SSLTermination-d1e2479.html) and HTTPS redirection. This updates the existing `rax_clb` module to add two new parameters:

 * `https_redirect` enables or disables HTTPS redirection. (Note that this can only be done for the HTTPS protocol, or for HTTP with SSL termination enabled and secure_traffic_only.
 * `ssl_termination` uses a dictionary to configure SSL termination. `private_key` and `certificate` are its required keys; `secure_port`, `enabled`, `intermediate_certificate`, and `secure_traffic_only` are also accepted.

The module is still idempotent: SSL termination and redirection will be enabled or disabled on existing load balancers as necessary. I also added the new keys to the documentation.

Here's an example call, from rackerlabs/developer.rackspace.com#415:

```yaml
- name: Provision production web load balancer
  rax_clb:
    credentials: ~/.rackspace_cloud_credentials
    name: "prod_{{ server_name }}"
    port: 80
    protocol: HTTP
    algorithm: ROUND_ROBIN
    type: PUBLIC
    timeout: 30
    region: "{{ lookup('env', 'RAX_REGION') | upper }}"
    ssl_termination:
      private_key: "{{ lookup('file', 'credentials/' + server_name + '.key') }}"
      certificate: "{{ lookup('file', 'credentials/' + server_name + '.crt') }}"
      secure_traffic_only: yes
    https_redirect: yes
    wait: yes
    state: present
  register: clb_prod
```

One caveat: to use either of these, I needed to add implicit `waits` in the middle of the module: one to wait for the initial balancer to become active, and another to wait for the SSL settings to be applied. You can't do it all at once, and load balancers are immutable until their state reaches "READY".

I'm all ears for feedback :wink:

/cc @sivel, @claco