Use ES7 class properties initializers

src/backends/github/AuthenticationPage.js

@@ -6,13 +6,9 @@ export default class AuthenticationPage extends React.Component {
     onLogin: React.PropTypes.func.isRequired
   };
 
-  constructor(props) {
-    super(props);
-    this.state = {};
-    this.handleLogin = this.handleLogin.bind(this);
-  }
+  state = {};
 
-  handleLogin(e) {
+  handleLogin = e => {
     e.preventDefault();
     let auth;
     if (document.location.host.split(':')[0] === 'localhost') {
@@ -28,7 +24,7 @@ export default class AuthenticationPage extends React.Component {
       }
       this.props.onLogin(data);
     });
-  }
+  };
 
   render() {
     const { loginError } = this.state;