fsroque

String does no longer have a to_a method, so photo.Keywords.to_a breaks for single tagged images. The solution was to use the [Kernel#Array](http://www.ruby-doc.org/core/classes/Kernel.html#M005989) method in app/models/photo.rb:70

Hi, the default parameters from K1 and B are set to 100 and 0.8 respectively in the function bm25_weight defined in nearest_neighbours.py. The literature suggests values between 0 and 3...