Added maxmin distance

And corrected some things in euclidean and jaccard distances.
Removing unnecessary clutter
Added pending specs for each distance measure
Fixed typos in required files
Added methods to module's scope
Updated specs and the euclidean distance

- Added support for calculating norms when given a single argument.
- Raises an exception when given two Arrays of different sizes.

The specs cover most of the functionality of Measurable#euclidean and
Measurable#euclidean_squared. Now I need to cover the other metrics!