Updated python versions in readme

Author: azmeuk

README.rst

@@ -12,7 +12,7 @@ to install::
 
     pip install WTForms-SQLAlchemy
 
-Python 2.7, 3.5, 3.6, 3.7 & 3.8 are supported.
+Python 3.6, 3.7 & 3.8 are supported.
 
 An example using Flask is included in ``examples/flask``.