Make grammar implementation repositories more friendly with tree-sitter Rust bindings

[racer161]

Adding a cargo.toml, build.rs, and a lib.rs allows grammar definitions to be added to Rust projects using the tree-sitter Rust bindings easily by adding one dependency to cargo:

[dependencies]
tree-sitter-javascript = { git = "https://github.com/racer161/tree-sitter-javascript" }

With this edition, the readme.md in tree-sitter/lib/binding_rust/ : https://github.com/tree-sitter/tree-sitter/tree/master/lib/binding_rust will compile without the need for a build.rs or any knowledge of the cc crate. There's also no need to upload these grammar repos to crates.io since they only expose C libraries.

Obviously, this would need to implemented for each grammar repository. I think this makes the most sense to foster support for the rust bindings since its a one time fix (most likely) without need for any further modification. I'd be willing to fork the Javascript, C and Rust repos as a trial so at least the readme in the rust bindings repo would work without knowledge of cc or building.

[maxbrunsfeld]

@racer161 Sorry for ignoring this PR. It wasn't because of anything wrong with the PR. At the time I was just not prepared to make a decision about whether our team could maintain this kind of thing, and then lost track of this out of indecision.

We might move forward with something like this soon.

[racer161]

@racer161 Sorry for ignoring this PR. It wasn't because of anything wrong with the PR. At the time I was just not prepared to make a decision about whether our team could maintain this kind of thing, and then lost track of this out of indecision.

We might move forward with something like this soon.

No prob I totally understand its a pretty sweeping change. I've just been using my own fork for my personal projects and it works well enough. Thanks for the update.

[maxbrunsfeld]

Ok, #141 implemented this.