Raises TypeError when you call an API method with invalid keyword arguments

Before this, it's confusing whether the API arguments are keyword arguments or
positional arguments. This should help that a bit.
Fixes Test
Merge pull request #102 from sudorandom/master

Raises TypeError when you call an API method with invalid keyword arguments
Refactor Managers

 * Moves managers to SoftLayer.managers
 * Moves manager tests to SoftLayer.tests.managers
 * Adds missing manager imports so that all managers are exposed as SoftLayer.ManagerClass
 * Adds missing hardware manager to the docs
 * Adds Firewall Manager Test
 * Renames capital manager modules to lowercase
 * Moves manager exceptions to SoftLayer.exceptions
 * Adds a couple missing module doc blocks
Merge branch 'move_managers' of github.com:sudorandom/softlayer-api-python-client into move_managers