Created tests for different cell types

Issue #21 

Created tests for each cell type and each changes the UI in some way

First Slider: Changes UITextField text to the value of the slider
First Name Cell: Changes the title of the nav bar to whatever you type in
Environments Cell: Displays a green circle on the screen when 'Production' is chosen (note: this default is stored as an ```NSNumber``` and not a string)
Purple Background Cell: Changes background of view to purple when switched on
This is basically duplicate code of the notify observers method. I'd factor out a method that just notifies *one* observer and then call it repeatedly in the loop within the method that notifies all the observers.