Toggle navigation between view controllers

I changed the title to say how many beers in parenthesis when the slider moves. 

I did this by adding `- (void)sliderValueDidChange:(UISlider *)sender;` to the header file for **ViewController.h**. Then line 136 in **ViewController.m** will show you the code I used to display the text in the title. In **WhiskeyViewController.m**, on line 18 is where I basically copy pasted the line of code from the ViewController to override it to say "Whiskey" in the title instead of "Wine"