r] = binaryTreeTrain( data, [pTree] )

 INPUTS
  data       - data for training tree
   .X0         - [N0xF] negative feature vectors
   .X1         - [N1xF] positive feature vectors
   .wts0       - [N0x1] negative weights
   .wts1       - [N1x1] positive weights
   .xMin       - [1xF] optional vals defining feature quantization
   .xStep      - [1xF] optional vals defining feature quantization
   .xType      - [] optional original data type for features
  pTree      - additional params (struct or name/val