docs: simplify and improve main module documentation

Remove the reference to the Feather nRF52840 Express, since this library
can be used on many boards now (eg. Circuit Playground BlueFruit).

Update BlueFruit Connect App link to point to Adafruit's main app web
page, rather than the iOS-specific page, since this app is available for
Andriod too now.

Remove the GitHub releases link and add a link to to circuitpython.org's
download page instead, because the GitHub release pages point there now.

Author: ktdreyer

adafruit_bluefruit_connect/__init__.py

@@ -23,24 +23,13 @@
 `adafruit_bluefruit_connect`
 ============================
 
-This module helps you to communicate with the Adafruit Bluefruit Connect app or use its protocols.
+This module helps you to communicate with the `Adafruit Bluefruit Connect App
+<https://learn.adafruit.com/bluefruit-le-connect>`_ or use its protocols with
+boards that run `Adafruit CircuitPython firmware
+<https://circuitpython.org/downloads>`_.
 
 * Author(s): Dan Halbert for Adafruit Industries
 
-Implementation Notes
---------------------
-
-**Hardware:**
-
-   Adafruit Feather nRF52840 Express <https://www.adafruit.com/product/4062>
-
-**Software and Dependencies:**
-
-* Adafruit Bluefruit LE Connect App
-  https://learn.adafruit.com/bluefruit-le-connect-for-ios (also available for Android)
-* Adafruit CircuitPython firmware for the supported boards:
-  https://github.com/adafruit/circuitpython/releases
-
 """
 
 # imports