CNN--modification

Hi, I have added some other useful activation function--hyperbolic tangent and max pooling layer. It can accelerate the convergence speed by a large margin. ( Apologize for the un professional pulling request--it is my first Github contribution! Hope I can contribute more to the society). 
And if you need more information, I would like to hear from you. Thank you again for this library.

Add: max pooling layer, matlab m-file and faster version C++  file (in mex compile version)
Add: hyperbolic tangent layer
Add: early stopping criteria