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
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
Merge pull request #100 from sudorandom/move_managers

Refactor Managers