PYTHONDC-9: Clean up documentation for streams read()
PYTHONDC-9: Clean up documentation for streams read()

The lists included originally were nice but they were not picked
up by sphinx.  Instead, we just list the possible values and point
to the device cloud documentation for users to find additional details.

michaelcho/python-devicecloud,digidotcom/python-devicecloud,brucetsao/python-devicecloud,brucetsao/python-devicecloud,digidotcom/python-devicecloud,ctrlaltdel/python-devicecloud,ctrlaltdel/python-devicecloud,michaelcho/python-devicecloud