Use Maxout

[americast]

Create an option to use Maxout in place of Sigmoid.

[Vaibhavdixit02]

Hey, I would like to work on this issue.

[JiviteshDebata]

@americast Thanks for providing a direction to proceed. Currently Sigmoid might cause a chunk of the network to become passive. Maxout does seem like the best solution but may I suggest implementing either tanh or ReLU(leaky) for the current code? '
Advantages will be:
1)replace the Sigmoid for something much better
2)It will be a simple drop in replacement for Sigmoid and might help in making/understanding maxout later.Also it will demonstrate a difference in using different activation functions.

[JiviteshDebata]

Made a PR for above ^