Fix SelectEventPlugin

mouseup was not fired when context menu showed, so select events stopped being fired.

Author: joshduck

src/eventPlugins/SelectEventPlugin.js

@@ -192,6 +192,7 @@ var SelectEventPlugin = {
  case topLevelTypes.topMouseDown:
  mouseDown = true;
  break;
+ case topLevelTypes.topContextMenu:
  case topLevelTypes.topMouseUp:
  mouseDown = false;
  return constructSelectEvent(nativeEvent);