Fix headnode_{create,delete}_hnic

First, fix the API.
Second, fix the typo in the CLI.

This should now work.

Closes #138
Generalize 'object_url' to take extra arguments

I used *args so that it would be backwards-compatible with previous usage.
The only difference, and it's minor, is that now all arguments are
urllib-quoted.  Tested with two- and three- argument calls.
Add TODO to fix name of object_url
Merge pull request #145 from gsilvis/cli-generalize-url

Generalize 'object_url' to take extra arguments
Add parameter 'nodename' to 'headnode_delete_hnic'
Add two more tests to headnode_delete_hnic
Merge branch 'devel' into bug138

Conflicts:
	haas/cli.py
Merge pull request #144 from gsilvis/bug138

Fix headnode_{create,delete}_hnic