Fix #221: no label on readded buttons

Author: chalup

library/src/main/java/com/getbase/floatingactionbutton/FloatingActionsMenu.java

@@ -197,6 +197,7 @@ public void addButton(FloatingActionButton button) {
   public void removeButton(FloatingActionButton button) {
     removeView(button.getLabelView());
     removeView(button);
+    button.setTag(R.id.fab_label, null);
     mButtonsCount--;
   }