Pixels 0.0.3 release

Thanks to the heroic efforts of community member @lovesegfault, pixels 0.0.3 is now available! This release updates the wgpu dependency to 0.5.0, bringing along several fixes by the gfx team.

One of the nicest improvements, from my perspective, is that pixels now works with SDL2 on macOS.

We've also refactored the source tree to cleanup dependencies for the examples. This has been a thorn in my side for a while, and I'm happy it's finally resolved in a nice manner.