Added Swift version of the code for better readability and just for the fun of it.

[eyaldar]

Hey, I stumbled upon your code while learning Swift and looking for clustering abilities, In order to better understand your solution I migrated your code to a Swift solution. As it is already implemented I thought others like me(people with no knowledge of the Objective-C language nor willing to learn it) might appreciate the ability to read the same code in the Swift language.