[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
There should be some utility function somewhere to do e.g. 
```
with capture_stdout as out:
    #do stuff
assert_true(out.getvalue() != '')
```
because if an exception is raised, then you might fail to restore sys.stdout. It's not an issue here, or I'd even claim in tests in general, since you should never get unexpected exceptions.