###Implementation of the Examples from the Book Programming Collective Intelligence in Ruby

The code in the book is presented in an imperative fashion, and that style is imitated in these implementations. This is not well factored code.

Notes:

1. Example one differs from the book per errors in the book's code.
2. Left out the creation of a dataset using del.icio.us.
3. The same error from the first example of euclidean distance happens again when calculating similar items.