RatingsOnline: rm unnecessary empty line
item online evaluation: rewrote protocol; now documented and simpler
BinaryData(As|S)ymmetricCorrelationMatrix.ComputeCorrelation(): throw NotImplementedException if necessary
add 'Who uses MyMediaLite?' tweet
add KNN to test_item_recommendation_online.sh
replace incremental update implementation by a more simple and efficient one
ItemAttributeKNN: rm unnecessary whitespace