"vector" package provides vector-operations required for perceptron learning.
"(*Classfier).weight is initialized with zero-sized zero vector.
Replace "Extend" with "Resize".
Fix: Replace "Vector" with "vector.Vector".
"(Vector).Resize" resizes the vector. If it become smaller, losts values stored in slice with higher index or become larger, fills by zeros.
"(Vector).NonZeros" is used for efficient calculation of "Add" and "Dot" between differnet vector types.
A vector becomes "undefined" with undefined operation, for example, "Add" between different size vectors.
"(Vector).Dot" should returns a float64 value.
Fix: Replace "v" with "iter.vector".
Merge branch 'feature/dense-vector'