Use system fonts on more platforms

This allows other platforms such as Windows, macOS and iOS to use their system fonts rather than downloading a copy of Roboto. It also makes the app feel a little closer to native on those platforms!

app/assets/javascripts/components/components/button.jsx

@@ -27,7 +27,7 @@ const Button = React.createClass({
 
   render () {
     const style = {
-      fontFamily: 'Roboto',
+      fontFamily: 'inherit',
       display: this.props.block ? 'block' : 'inline-block',
       width: this.props.block ? '100%' : 'auto',
       position: 'relative',