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
I wouldn't change the input parameter. This might be suprising to the user.
This might be infer directly in the _compute_hidden_activations functions.

Otherwise, we often add a self.gamma_ attribute whenever we infered parameter values;