Fix deprecation warning
Fix deprecation warning

This change will resolve the deprecation warning shown below:
flask_io/utils.py:2: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3, and in 3.9 it will stop working
    from collections import Mapping, Sequence
viniciuschiele/flask-binding,viniciuschiele/flask-io