Change bpm to be a float (instead of int) field

[baelany]

Description

Fixes issue #4298 .
To address the feature outlined in issue #4298, we modified beets/library.py and beetsplug/bpm.py to have bpm support float type instead of integer type. We locally tested our changes by making modifications to test/test_beatport.py and test/test_query.py.

To Do

• Documentation. (If you've add a new command-line flag, for example, find the appropriate page under docs/ to describe it.)
• Changelog. (Add an entry to docs/changelog.rst near the top of the document.)
• Tests. (Encouraged but not strictly required.)

[sampsyo]

Thank you for getting this going!!

This is a somewhat sensitive change, so we will want to proceed with caution. In particular, there are two potential pitfalls on my mind:

• If someone has an existing library with a bunch of integer bpm values, will using that database with the new version of beets cause any problems?
• We will want to change MediaFile to use float also. Will it cause any problems for the two to temporarily disagree on the type of the field? Or do we need to make a coordinated change—updating MediaFile, releasing a new version, and changing beets' dependencies to require the updated version of MediaFile before release?

I would love any help thinking through these issues in detail!

[stale]

Is this still relevant? If so, what is blocking it? Is there anything you can do to help move it forward?

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.