Create a Category

[joshdbarton]

As an admin I would like to be able to create a new category so that I can give authors the ability to better classify their posts.

Given an admin is on the Category list page
When they select the Create Category button
Then they should be directed to a form in which they can enter a new category name

Given an admin has entered a Category name
When they click the Save button
Then a new category should be saved to the database
And the admin should be directed to the Category list page

NOTE: For the time being it is acceptable to treat all users as admin users. There is a future story about enforcing user permissions.