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
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> I am now solving the system using scipy.linalg.solve, is this more efficient? Thanks
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did you bench? I recommend you have a look at how the ridge is solved and
maybe see how it can be reused (if it can). I would say profile / bench to
see what's the best way to solve the linear systems in this PR.