Update python version in README

Signed-off-by: Matthew Peveler <[email protected]>

README.rst

@@ -23,7 +23,7 @@ then runs pylint on all discovered `.py` files.
 Dependencies
 ------------
 
-- Python 3.5+
+- Python 3.7+
 - `colorama <https://pypi.org/project/colorama/>`_
 - `pylint <https://pypi.org/project/pylint/>`_
 - `pytest <https://pypi.org/project/pytest/>`_ (for testing)