Fix diff response when path ends with or without slash

This fixes the following problem:
- When a client makes a GET to `http://domain/api/apps`, easymock looks for `/api/apps_get.json`.
- But when a client makes a GET to `http://domain/api/apps/` *with an ending slash*, easymock looks for `/api/apps/_get.json`.

With this fix, easymock will always look for `/api/apps/_get.json`, which I think is much more clear.