Get QuantileLoss to work

[isaacmg]

We want to add support for the QuantileLoss function. It is currently already in the loss function code. However, at this point it just needs to be added to the loss dictionary and properly commented so users know how to use it. In the future we may want to add automatic quantile calculation but save that for another day. Anyways good first issue.

• Add QuantileLoss to the dictionary
• Add integration test using QuantileLoss for one of the models