Merge pull request #46 from slootsky/feature/add_PortalBase_to_Dependencies_in_README

added PortalBase to Dependencies

Author: makermelissa

README.rst

@@ -25,6 +25,7 @@ Dependencies
 This driver depends on:
 
 * `Adafruit CircuitPython <https://github.com/adafruit/circuitpython>`_
+* `Adafruit PortalBase <https://github.com/adafruit/Adafruit_CircuitPython_PortalBase>`_
 
 Please ensure all dependencies are available on the CircuitPython filesystem.
 This is easily achieved by downloading