adds note about configuring fuel's data_path var

[bmabey]

I had never used fuel before so I was a bit confused when I ran into an exception about a missing config file. This updates the README to help future users know where to look to configure fuel before using this library.

[bmabey]

Okay, it looks like kerosense is overriding the fuel data path anyways. In that case this update may not be worth merging in. Rather, it is probably better to fix kerosense so that the following exception is avoided for new installs:

Traceback (most recent call last):
  File "examples/cifar10.py", line 8, in <module>
    from kerosene.datasets import cifar10
  File "/home/bmabey/.../kerosene/examples/kerosene/datasets/cifar10.py", line 3, in <module>
    from .dataset import Dataset
  File "/home/bmabey/.../kerosene/examples/kerosene/datasets/dataset.py", line 11, in <module>
    initial_fuel_config_path = fuel.config.data_path
  File "/home/bmabey/.conda/envs/.../lib/python3.5/site-packages/fuel/config_parser.py", line 150, in __getattr__
    "provided: {}.".format(key))
fuel.exceptions.ConfigurationError: Configuration not set and no default provided: data_path.

[dribnet]

Thanks for this, I'm glad to see someone getting some use from this library.

Yes, the intention was that kerosene would handle the fuel path internally. But I think the conventions for how fuel treats this path changed from a string to a list of strings. I can look into this and try to update this code to work with the latest versions of fuel.

[dribnet]

Sorry for not getting to this. I still think the right fix would be to update the kerosene path is a list of strings, which I think is the newer fuel convention. I would welcome a merge request to this effect or might have time in the coming weeks to test this myself.