Making sure the user knows they're using the PublicAPI

[allerter]

As you know, the PublicAPI (or the Web API as Genius calls it) isn't officially supported by Genius and not only may change without notice, users that send a lot of requests might hit 403 errors. Even IPs that Genius considers to be a bot might get hit a 403 error. That might be okay for some, but the user should be aware that they're using a part of the API that isn't part of the official Developers API.
My suggestion is to add a parameter called use_public_api to Genius.__init__ with the default value of False. Whenever the user tries to use a method that either directly or indirectly uses the Public API, we'll check the value of the attribute to see if we can use the Public API or not.

>>> genius = Genius(TOKEN, use_public_api=False)
>>> genius.search_artist("Eminem")

Searching for songs by Eminem...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "lyricsgenius\genius.py", line 525, in search_artist
    artist_id = artist_id if artist_id else find_artist_id(artist_name)
  File "lyricsgenius\genius.py", line 510, in find_artist_id
    response = self.search_all(search_term)
  File "lyricsgenius\api\public_methods\search.py", line 210, in search_all
    raise Exception("Can't use Public API method `search_all` unless"
Exception: Can't use Public API method `search_all` unless `genius.use_public_ap
i=True`.
Read more at ...

[johnwmillr]

I like this suggestion, especially use_public_api defaulting to False.

[allerter]

Added #212.