Docs: wrong/outdated code snippet at Zoo documentation

## Due Date
*To be completed by:* YYYY-MM-DD

## Description
I tried the example at https://deeplearning4j.org/model-zoo, i.e. ```ZooModel zooModel = new AlexNet(..); MultiLayerConfiguration net = zooModel.conf(); ```
Sadly, the ```conf()``` method is not part of the ```ZooModel``` class. I use 1.0.0-alpha.

I want to use the zoo model for regression somehow, and the idea was to change the output layer with the configuration accordingly. Now there is no general, thus configurable possibility left for this.
Best would be a 'regression switch'/flag for the zoo models, e.g. 'setRegression(true)' in class ZooModel.

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