Added Fitbit OAuth 2 Mobile Application Flow example

docs/examples/examples.rst

@@ -8,6 +8,7 @@ Examples
    github
    google
    facebook
+   fitbit
    linkedin
    outlook
    tumblr

docs/examples/fitbit.rst

@@ -0,0 +1,40 @@
+.. _fitbit:
+
+Fitbit OAuth 2 (Mobile Application Flow) Tutorial
+=================================================
+
+This makes use of the Implicit Grant Flow to obtain an access token for the `Fitbit API`_. Register a new client application there with a callback URL, and have your client ID handy. Based on an `another example`_ of the Mobile Application Flow. 
+
+.. _`Fitbit API`: https://dev.fitbit.com/
+.. _`another example`: https://github.com/requests/requests-oauthlib/issues/104
+
+.. code-block:: pycon
+
+    >>> import requests
+    >>> from requests_oauthlib import OAuth2Session
+    >>> from oauthlib.oauth2 import MobileApplicationClient
+
+    # Set up your client ID and scope: the scope must match that which you requested when you set up your application.
+    >>> client_id = "<your client ID here>"
+    >>> scope = ["activity", "heartrate", "location", "nutrition", "profile", "settings", "sleep", "social", "weight"]
+
+    # Initialize client
+    >>> client = MobileApplicationClient(client_id)
+    >>> fitbit = OAuth2Session(client_id, client=client, scope=scope)
+    >>> authorization_url = "https://www.fitbit.com/oauth2/authorize"
+
+    # Grab the URL for Fitbit's authorization page.
+    >>> auth_url, state = fitbit.authorization_url(authorization_url)
+    >>> print("Visit this page in your browser: {}".format(auth_url))
+
+    # After authenticating, Fitbit will redirect you to the URL you specified in your application settings. It contains the access token.
+    >>> callback_url = input("Paste URL you get back here: ")
+
+    # Now we extract the token from the URL to make use of it.
+    >>> fitbit.token_from_fragment(callback_url)
+
+    # We can also store the token for use later.
+    >>> token = fitbit['token']     
+
+    # At this point, assuming nothing blew up, we can make calls to the API as normal, for example:
+    >>> r = fitbit.get('https://api.fitbit.com/1/user/-/sleep/goal.json')