Use Lists for menu items, instead of maps or sequences.

Maps are actually invalid, and lists make more sense than sequences.

src/components/AppHeader/AppHeader.js

@@ -88,7 +88,7 @@ export default class AppHeader extends React.Component {
           onHide={this.handleCreateMenuHide}
         >
           {
-            collections.filter(collection => collection.get('create')).valueSeq().map(collection =>
+            collections.filter(collection => collection.get('create')).toList().map(collection =>
               <MenuItem
                 key={collection.get("name")}
                 value={collection.get("name")}

src/components/Widgets/Markdown/MarkdownControl/Toolbar/ToolbarComponentsMenu.js

@@ -41,7 +41,7 @@ export default class ToolbarComponentsMenu extends React.Component {
           onHide={this.handleComponentsMenuHide}
           ripple={false}
         >
-          {plugins && plugins.map(plugin => (
+          {plugins && plugins.toList().map(plugin => (
             <MenuItem
               key={plugin.get('id')}
               value={plugin.get('id')}