* Mish activation function and its derivative Signed-off-by: raver119 <raver119@gmail.com> * signature fix Signed-off-by: raver119 <raver119@gmail.com> * mish as activation for dl4j Signed-off-by: raver119 <raver119@gmail.com> * javadoc Signed-off-by: raver119 <raver119@gmail.com> * minor optimization Signed-off-by: raver119 <raver119@gmail.com>