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
The code seems to be less nested and easier to understand. The first call variable doesn't seems to be necessary:

```
first_call = (self.algorithm == 'standard' or self.algorithm == 'recursion_lsqr' and (not warm_start or self._H_sub is None))
```