Update itunespy to 1.6.0

[pyup-bot]

This PR updates itunespy from 1.5.5 to 1.6.0.

Changelog

1.6

Thanks to the wonderful codello who did all the amazing work in this release! 👍 

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- 🔥 **Breaking**: This version and further versions of `itunespy` will **NOT** support any Python version below 3.5. If you need to use this library in any other version you can use `itunespy <= 1.5.5` but those won't get any support or new features.
- 🔥 **Breaking**: `__repr__` now returns a different value (see below) so make sure you don't use this in a non-compatible way before updating.
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- 😄 Type hints are now available throughout the code
- 😄 `collection_type`, `artist_type` and `track_type` are now available in a `ResultItem` even if it does not have a `wrapperType`. This is to provide a more consistent interface allowing to query arbitrary fields in a result.
- 😄 `__repr__` now returns  returns the underlying JSON object of a `ResultItem`.
- 😄 `ResultItem` now has a `get_country()` method for converting between country code formats via `pycountry`.
- 🐛 The country specified in a query is now preserved in any sub-query. Example: Specifying a country via `search_artist` will now retain that same country when doing a `get_albums`.
- 🐛 Performing lookups and searches does not raise an error anymore if the `artist_amg_id` or `ups` is not a `str` (at least in some cases).
- 🐛  Fixed cases in which special characters in search terms or other query parameters would not be properly escaped.

Links

• PyPI: https://pypi.org/project/itunespy
• Changelog: https://pyup.io/changelogs/itunespy/
• Repo: http://github.com/spaceisstrange/itunespy