Adding ai4r

Provides lots of AI algorithms.

Using for clustering now, but I imagine we'll use
some ML or classifiers in the future too
First commit of clustering code.

Just does basic clustering.  No tuning, and no attempt to rank
clusters, so we know which tier is 'better' than the other.

Also, is only using the total_points to cluster.

Would be trivial to add more dimentions to the data, rather than
just using the total.
Use new tiers in index view
Added running rake api:tier to the instructions