fix heroku button
fix heroku button

patrickxie/invengine,gaearon/flask-react-boilerplate,gaearon/flask-react-boilerplate,zachwooddoughty/react-playground,catalinmiron/flask-react-boilerplate,catalinmiron/flask-react-boilerplate,alexkuz/flask-react-boilerplate,zachwooddoughty/react-playground,patrickxie/invengine,sellds4/flask-react-boilerplate,zachwooddoughty/react-playground,alexkuz/flask-react-boilerplate,patrickxie/invengine,sellds4/flask-react-boilerplate