[MRG] 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
Those two lines should be rewritten in a for loop to use `self.batch_size` when not `None` in order to make it possible to control the memory usage at prediction time when both `n_samples` and `n_hidden` are large but `n_output` is small.