add nv_vecotr_mean & nv_vector_var
fix bug in nv_vector_var
fix bug in nv_matrix_m
replace nv_gemv with nv_matrix_mulv; add nv_matrix_mul; refactor
version update
add nv_vector_div & nv_vector_divs
fix bug in nv_vector_divs
fix bug in nv_matrix_var & nv_matrix_mean
fix bug in nv_cov & refact
add support for dropout in nv_mlp