Adds Token-based Auth

This adds the ability to use username/password based auth to get an
auth token to use for subsequent calls.

  import SoftLayer
  client = SoftLayer.Client()
  client.authenticate_with_password('username', 'password')

  import SoftLayer
  client = SoftLayer.Client()
  # Get all security questions (you basically pick one at random that you have answered)
  client['User_Security_Question'].getAllObjects()
  client.authenticate_with_password('username', 'password', 122, '2004')

note: this is pending an API release to add this feature to the XML-RPC API.
Fixes a test
Merge pull request #114 from sudorandom/token_auth

Adds Token-based Auth