Added info about caching to the documentation

docs/caching.rst

@@ -0,0 +1,18 @@
+Caching datasets locally
+========================
+
+In some use cases, it may be desirable to set Fuel's ``data_path`` to
+point to a shared network drive. For example, when configuring multiple
+machines in a cluster to work on the same data in parallel.
+However, this can easily cause network bandwidth to become saturated.
+
+To avoid this problem, Fuel provides a second configuration variable
+named ``local_data_path``, which can be set in ``~/.fuelrc``. This
+variable points to a filesystem directory to be used to act as a local
+cache for datasets.
+
+This variable can also be set through an environment variable as follows:
+
+.. code-block:: bash
+
+    $ export FUEL_LOCAL_DATA_PATH="/home/username/my_local_cache"

docs/index.rst

@@ -11,6 +11,7 @@ Welcome to Fuel's documentation!
    new_dataset
    extending_fuel
    server
+   caching
    api/index
 
 Fuel is a data pipeline framework which provides your machine learning models