Setting per_page > 40 omits results

Running

```
workouts = mmf.workout.search(user=xxx,per_page=40)
```

works fine, giving multiple pages with 40 workouts each.  But passing

```
workouts = mmf.workout.search(user=xxx,per_page=10000)
```

gives back just one page of 40 workouts, even though `workouts.count` is greater than 40.

By the way, thanks for creating this package!
