implemented padding aware im2col and col2im functions
add test code to test the padding aware im2col col2im functions
add code to measure timing
add convert_cifar_float_data in example for float rather than uint8
implemented cccp layer
add from_file filler and from_binary filler
dropout scale on test time
random dropout support during test pass
add mean_on_train, so that dropout is fully controlable for debugging
add global_pooling layer