Rust Parser Build Instructions

First, you need to install Rust. Check if your OS comes with a Rust version, if not, go to this link and run the one-liner to install.
To make the Rust parser available to Python, I used the PyO3 bindings. Its Python-based build tool is maturin.
Go into your preferred venv or conda env, and simply install it with pip install maturin.
Build the genpa-rs library (which exports the fast Earley parser) by running
```
$ maturin develop
```
Test your build in Python:
```
$ python
>>> from genpa_rs import Earley
>>> Earley
<class 'builtins.Earley'>
```
- Note: Make sure you run any maturin develop commands in the Python environment where you intend to run the GenParse code. Binaries built for a specific Python version might not run in another!
The above actually builds a debug version build and will be hella slow. Run
```
$ maturin develop --release
```
to build with Rust compiler's optimizations enabled.
Finally, to run the tests for the Rust parser's Python interface, run
```
$ python genparse/experimental/test_earley_fast.py
```

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