The biggest version bump is Amethyst from 0.12 to 0.13. This has a
breaking change in the example, where world.read_resource now returns
a Fetch<ScreenDimensions> instead of a &ScreenDimensions.
* Update README.md
Add OSX shader compiling instructions caveats.
* Update README.md
Move change to Mac section because it did not need to be 2 sections.
0.12 was just released, so template can be updated. No need for render graph anymore, just uses render plugins, and ran cargo update to get rendy minor version