reword warning, add doc link

Author: CaseyFaist

bin/steps/python

@@ -35,9 +35,10 @@ else
           echo "       Using supported version of Python 3.6 ($PYTHON_VERSION)"
         fi
       else
-        puts-warn "Heroku supports the latest version of Python 2 $LATEST_37, Python 3.6 $LATEST_36 and Python 3.7 $LATEST_2." 
+        puts-warn "Heroku supports runtime versions $LATEST_37, $LATEST_36 and $LATEST_2." 
         puts-warn "You are using $PYTHON_VERSION, which is unsupported."
         puts-warn "We recommend upgrading by specifying the default supported version ($LATEST_36)."
+        echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
       fi
     fi
   fi