Upgrade to React Router v4 (#667)

* Upgrade to React Router v4

* Fix pages not change when the URL was changed.

This issue is due to the Redux `connect` wrapper around `<App/>`.
`connect` diffs changes in regular props to know when to update the
component, but doesn't check context props like `location`.
See
https://github.com/ReactTraining/react-router/blob/master/packages/react-router/docs/guides/blocked-updates.md.

* Update to new `history` methods.

src/components/AppHeader/AppHeader.js

@@ -1,7 +1,7 @@
 import PropTypes from 'prop-types';
 import React from "react";
 import ImmutablePropTypes from "react-immutable-proptypes";
-import { IndexLink } from "react-router";
+import { Link } from 'react-router-dom';
 import { IconMenu, Menu, MenuItem } from "react-toolbox/lib/menu";
 import Avatar from "react-toolbox/lib/avatar";
 import AppBar from "react-toolbox/lib/app_bar";
@@ -66,9 +66,9 @@ export default class AppHeader extends React.Component {
         onLeftIconClick={toggleDrawer}
         onRightIconClick={this.handleRightIconClick}
       >
-        <IndexLink to="/" className={styles.homeLink}>
+        <Link to="/" className={styles.homeLink}>
           <FontIcon value="home" className={styles.icon} />
-        </IndexLink>
+        </Link>
         <IconMenu
           theme={styles}
           icon="add"

src/components/UnpublishedListing/UnpublishedListing.js

@@ -2,7 +2,7 @@ import PropTypes from 'prop-types';
 import React from 'react';
 import { DragSource, DropTarget, HTML5DragDrop } from 'react-simple-dnd';
 import ImmutablePropTypes from 'react-immutable-proptypes';
-import { Link } from 'react-router';
+import { Link } from 'react-router-dom';
 import moment from 'moment';
 import { capitalize } from 'lodash'
 import { Card, CardTitle, CardText, CardActions } from 'react-toolbox/lib/card';