Update implement-queue-using-stacks.py
Update implement-queue-using-stacks.py

It requires an integer result value from pop now.
Maybe the question has been changed.

```
    def pop(self):
        """
        Removes the element from in front of queue and returns that element.
        :rtype: int
        """
```
tudennis/LeetCode---kamyu104-11-24-2015,kamyu104/LeetCode,tudennis/LeetCode---kamyu104-11-24-2015,kamyu104/LeetCode,kamyu104/LeetCode,kamyu104/LeetCode,tudennis/LeetCode---kamyu104-11-24-2015,tudennis/LeetCode---kamyu104-11-24-2015,tudennis/LeetCode---kamyu104-11-24-2015,kamyu104/LeetCode