add note to install.rst about how to run tests

docs/source/install.rst

@@ -25,12 +25,42 @@ dependencies you would like to keep up to date:
 *   ``pip install dask``: Install only dask, which depends only on the standard
     library.  This is appropriate if you only want the task schedulers.
 
-Source
-------
+We do this so that users of the lightweight core dask scheduler aren't required
+to download the more exotic dependencies of the collections (numpy, pandas,
+etc..)
+
+Install from Source
+-------------------
 
 To install dask from source, clone the repository from `github
 <https://github.com/dask/dask>`_::
 
     git clone https://github.com/dask/dask.git
     cd dask
     python setup.py install
+
+or use ``pip`` locally if you want to install all dependencies as well::
+
+    pip install -e .[complete]
+
+You can view the list of all dependencies within the ``extras_require`` field
+of ``setup.py``.
+
+
+Test
+----
+
+Test dask with ``py.test``::
+
+    cd dask
+    py.test dask
+
+Although please aware that installing dask naively may not install all
+requirements by default.  Please read the ``pip`` section above that discusses
+requirements.  You may choose to install the ``dask[complete]`` which includes
+all dependencies for all collections.  Alternatively you may choose to test
+only certain submodules depending on the libraries within your environment.
+For example to test only dask core and dask array we would run tests as
+follows::
+
+    py.test dask/tests dask/array/tests