This patch adds a new `tree-sitter-loader` crate, which holds the CLI's
logic for finding and building local grammar definitions at runtime.
This allows other command-line tools to use this logic too!
This patch updates the CLI to use anyhow and thiserror for error
management. The main feature that our custom `Error` type was providing
was a _list_ of messages, which would allow us to annotate "lower-level"
errors with more contextual information. This is exactly what's
provided by anyhow's `Context` trait.
(This is setup work for a future PR that will pull the `config` and
`loader` modules out into separate crates; by using `anyhow` we wouldn't
have to deal with a circular dependency between with the new crates.)
* Rename parse_str to parse and make it polymorphic.
* Rename parse_utf8 to parse_with, since it is now the callback-based
version of parse
* Add a parse_utf16 method analogous to parse
* Rename existing parse_utf16 method to parse_utf16_with
This brings in the changes from tree-sitter/rust-tree-sitter#5
* Structure `cli` crate as both a library and an executable, so that
benchmarks can import code from the crate.
* Import macros in the Rust 2018 style.
