Fix manhattan distance calculation
Add Chebyshev and Cranberra distances, improve Manhattan distance

Previously, Manhattan distance measure was only able to calculate
vector distances. Now, it's possible to calculate distances on
matrices, too, without unnecessary overhead of copying vectors,
doing an in-place lookups.
Run goftm on all files ti fix indentation
Remove unused subVector calls
Change wording for Eucledian Distance comments
Merge branch 'feature/ifesdjeen/distances2' of https://github.com/sjwhitworth/golearn into optimisation
Refactored KNN to implement the estimator interface