GSoC 2014: Standard Extreme Learning Machines

Finished implementing the standard extreme learning machines (ELMs). I am getting the following results with 550 hidden neurons against the digits datasets,

Training accuracy using the logistic activation function: 0.999444
Training accuracy using the tanh activation function: 1.000000

Fortunately, this algorithm is much easier to implement and debug than multi-layer perceptron :).
I will push a test file soon.

@ogrisel , @larsmans
Given `n` batches and let's say we are now in the **5-th batch**. `self._H_sub` should represent the hidden activations of **batch 0 ** to **batch 5** combined. Anyhow, subset doesn't really make sense indeed. I would call it `_H_inter` which means `hidden_activations_intermediate`. What do you think?
Thanks