change sequence of assignment in app#route

if no ```verb``` argument is applied in ```app.route(verb, path)```, the code snippet below mistakes in assignment  sequence:
```
// if the method signature is just (path, callback)
// assume the verb is 'any'
  if (callback.length === 0 && _isFunction(path)) {
    path = verb;
    callback = [path];
    verb = 'any';
  }
```