Topsy

This is a compatibility fix for wgpu v0.13.0.

The version of wgpu is now pinned, since the API continues to evolve.

**Full Changelog**: https://github.com/pynbody/topsy/compare/v0.3.1...v0.3.3

What's Changed

This version introduces a GUI with a toolbar for e.g. changing the colormap and quantity visualised, and support for exporting movies.

It also fixes a bug with the mip-mapping that could lead to incorrect results on some GPU architectures.

**Full Changelog**: https://github.com/pynbody/topsy/compare/v0.2.0...v0.3.1

This version is almost a complete re-implementation over 0.1.x, using wgpu instead of OpenGL, but presents a similar interface.

In terms of features there are two changes

* Ability to show images of arbitrary quantities such as temperature (weighted by column density); pass `-q` on command line
* Ability to embed and manipulate within a jupyter notebook, with rendering performed on the server

See the updated README.md for more information

Fix minimum version of pillow

This is a very rough minimal functionality alpha release in case anyone wishes to see what's going on