remove one_hot, first try

If you don't pass `y_labels` to the `DenseDesignMatrix` class the data will be interpreted as a `VectorSpace`, which is correct for regression data. So, in this file you need to do something like:
```python
if self.task == 'regression':
     super(CSVDataset, self).__init__(X=X, y=y)
else:
     super(CSVDataset, self).__init__(X=X, y=y, y_labels=y_labels)
```