Documentation paper-cuts

[bspeice]

Very excited to make use of this, hit a couple minor snags when getting started.

README.md mentions installing with the following command-line:

cargo install --git https://github.com/rust-gpu/cargo-gpu

This has issues for me at the moment:

PS C:\...\draw-compute> cargo install --git https://github.com/rust-gpu/cargo-gpu
    Updating git repository `https://github.com/rust-gpu/cargo-gpu`
error: multiple packages with binaries found: cargo-gpu, spirv-builder-cli, xtask. When installing a git repository, cargo will always search the entire repo for any Cargo.toml.
Please specify a package, e.g. `cargo install --git https://github.com/rust-gpu/cargo-gpu cargo-gpu`.

README.md also mentions the template project as a separate crate here, but the crate in this repository may do a better job of explaining some of the features. Not sure if having two shader-crate-template examples was intended.

Will file some PR's in a bit, just wanted to make sure I opened an issue to track this.

[bspeice]

Closing now that #59 and #60 have been merged.