Error in fetch if collection's url is a method

[ami7ava]

Fetching a collection throws error if the collection'l url is a method, not property.

Here is a jsfiddle to demonstrate the issue.

[wyuenho]

Care to provide a PR? This one should be easy.

[ami7ava]

@wyuenho I hope the PR is good. Just not sure about the test I've added. As I am not quite familiar with qunit, so copied the previous test and changed the url to a method to check if it passes.