Added distance algorithms implementations

Hi all,

I added Lua implementations and tests for the following distance measures:
* [Euclidean](http://en.wikipedia.org/wiki/Euclidean_distance)
* [Manhattan](http://en.wikipedia.org/wiki/Manhattan_distance)
* [Chebyshev](http://en.wikipedia.org/wiki/Chebyshev_distance)
* [Minkowski](http://en.wikipedia.org/wiki/Minkowski_distance)

Tags have also been included.

Regards,
Roland.