Trim '?<key>' when extracting ID from HTTP URLs
Trim '?<key>' when extracting ID from HTTP URLs

If this excess part isn't trimmed from the ID, it can cause unexpected
results when calling some API methods.

For example; this code now correctly returns all albums for an artist:
```
artist = 'https://open.spotify.com/artist/7oPftvlwr6VrsViSDV7fJY?si=M3PrzRC4TBOZu8YyLYc-tA'
artist_albums = sp.artist_albums(artist)
```

Previously, this code mimicked same behaviour as calling
`spotify.artist`, but now will return albums as expected
with this commit.

Fixes #365 and #323.

plamere/spotipy