[WIP] Add form and JS for managing cookbook urls.

* Rename 'external_url' to 'source_url' on Cookbook.
* Add 'issue_url' attribute to Cookbook.
* Create form and JS for handling ajax:success and ajax:failure for the form

Next steps:

* create the update action for cookbooks
* make sure the UI is good to go

Notes:

* for some reason the [x] on the alert box is not working, not sure why
Continue working on cookbook URL management.

plz don't kill me for console.log

todo:

- remove console.log()s
- handle failures, aka display a useful error
- write feature spec
- make sure the UI is ok
Simply cookbooks_controller_spec cookbook let.
Set the cookbook urls on update.
Update the notices when updating cookbook urls.
Document the update action.
Remove unfinished failure specs.
Create cookbook manage feature spec.
Clean up the cookbookShow JS.

- improve the errors
- remove unneeded comments
Allow foundation alert-boxes to close with manage urls.
Update manage cookbook spec to pass. DOH.
Change where the alert-box gets appended.

With the new UI, this changes a little bit. :)
Add URL validations for source and issues urls on Cookbooks.
Adjust for external_url attribute change. [still more todo]
Let's temporarily remove url validation.