Cosmetic changes to make the code closer to prescribed Swift

Liked your code. I thought it could be slightly improved with a few edits here and there. My apologies for the myriad comments, I tend to commit my code in small chunks. Also fixed a couple of minor bugs 1) The Alert View titles were all "Success" even though there were strings for each case and 2) The switch's default case might have caused problems later on and wasn't needed since the switch block was exhaustive to begin with. Cheers!