Add API endpoint for destroying cookbook versions

:fork_and_knife: Adds API endpoint for destroying a single cookbook version.
I think partials end up being more reusable if they reference local variables instead of instance variables in the controller.  With instance vars, you need to make sure that whatever controller action is reusing the partial has the same variables, with the same names, but if you pass those instance vars into the partial as locals, it ends up being a bit more flexible, imo.  I just ran into this issue with the contingent cookbooks stuff I've been working on.  Do you have any thoughts on that?