HW1-2: Fix bug for categories

* Added controller spec to test for proper handling of categories new action
* Implemented fix for broken categories new action

* TODO: get all cucumber scenarios to pass for categories.
HW1-2: added more cucumber scenarios for testing categories admin features.

* Tests work fine for creating a new category and confirming it exists.
* However, there is a problem when I try to submit a form with a checkbox
* checked. The value posted in the params for the checkbox is embedded
* in quotes and an extral level of array.  The controller doesn't know what
* to do with this strange param, so it breaks.  I don't know how to fix this,
* as I'm just using the standard check functionality of capybara. The actual
* checkbox functionality works fine on the web page, so this is just an issue
* with the test setup.