Added more logging and fixed docs for search endpoint (#609)

* Added an exception clause that catches `FileNotFoundError` and logs a debug message in `SpotifyOAuth.get_cached_token`, `SpotifyPKCE.get_cached_token` and `SpotifyImplicitGrant.get_cached_token`.

* Changed docs for `auth` parameter of `Spotify.init` to `access token` instead of `authorization token`. In issue #599, a user confused the access token with the authorization code.

* Updated CHANGELOG.md

* Removed `FileNotFoundError` because it does not exist in python 2.7 (*sigh*) and replaced it with a call to `os.path.exists`.

* Replaced ` os.path.exists` with `error.errno == errno.ENOENT` to supress errors when the cache file does not exist.

* Changed docs for `search` to mention that you can provide multiple multiple types to search for. The query parameters of requests are now logged. Added log messages for when the access token and refresh tokens are retrieved and when they are refreshed. Other small grammar fixes.

* Removed duplicate word "multiple" from CHANGELOG

Co-authored-by: Stéphane Bruckert <stephane.bruckert@gmail.com>

CHANGELOG.md

@@ -13,6 +13,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - moved os.remove(session_cache_path()) inside try block to avoid TypeError on app.py example file
 - A warning will no longer be emitted when the cache file does not exist at the specified path
 - The docs for the `auth` parameter of `Spotify.init` use the term "access token" instead of "authorization token"
+- Changed docs for `search` to mention that you can provide multiple types to search for
+- The query parameters of requests are now logged
+
+### Added
+
+- Added log messages for when the access and refresh tokens are retrieved and when they are refreshed
 - Support `market` optional parameter in `track`  
 
 ## [2.16.1] - 2020-10-24