Fix for white background on menu table cells with the iOS7 SDK

Just wanted to start off by saying this is a pretty slick menu, thanks.

When building with the iOS7 SDK though, the menu's table cells have a white background:

![White menu table cells with iOS7 SDK](https://dl.dropboxusercontent.com/u/1525722/iOS7Menu/white-menu-bg-with-ios7-sdk.png "White menu table cells with iOS7 SDK")

This pull request contains a small tweak to fix it.