Edit a Tag

[hannahhall]

As an admin I would like to be able to modify a Tag so that I can rephrase the name if I think of something more appropriate.

Given the user is viewing the Tag list
When they select the option to edit an Tag
Then the user should be directed to a form and given the ability to change the Tag's name

Given the user is finished updating the Tag information
When they click the Save button
Then the updated Tag should be saved to the database
And the user should be redirected to the new Tag List page

Given the user has decided not to edit the Tag
When they click the Cancel button
Then the user should be redirected back to the 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.