The default values of INS_NUM and TEST_NUM lead to overfitting

[mjuarezm]

There is a mismatch between go-knn and Wang-kNN on how the number of instances for train/testing is initialized. Tao sets INST_NUM=60 and TEST_NUM=30 (lines 16 and 17 of flearner.cpp in https://crysp.uwaterloo.ca/software/webfingerprint/knn.zip). It seems go-knn is a port of a different version of flearner.cpp found in https://crysp.uwaterloo.ca/software/webfingerprint/attacks.zip.

The problem is that the INST_NUM is interpreted as the total number of instances per class in go-knn, while in Wang-kNN it's defined as the number of training instances for each class. The result is that the same set of instances is used for training and testing.

[mjuarezm]

Fixed in #3