Link manipulation in random() method

[DDimitris]

The foaas author, provides a list of fields on every action returned through the json. Instead of manipulating links to find the fields in the random() method, the fields from the json response should be used. Thus the only method that will manipulate links will be the build_url() method.

Note:

In FuckingOperations() class, a method must be added to return all the fields after the first request to operations is estalblished.