This breaking release drops the "neopixel" (an Adafruit trademark) package from this library so that Adafruit can re-purpose it for their own projects. See #8.
Don't worry- this was just a legacy compatibility shim and you can substitute import neopixel for import rpi_ws281x and everything will continue to work. There are no functional changes in this release.
Sorry for any inconvenience this might cause your project- if you're using import neopixel, since there are no bug fixes or improvements, you may continue to use v3.1.0 until you are ready to migrate.