[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
I would rather like to have the constructor only store the hyper parameters and initialized the pulic and private attributes in `_fit` using `hasattr(self, attribute_name)` test if required. In particular `coef_hidden_` and `coef_output_` should not be reset / reinitialized if `self.warm_start` is `True`.