GCRA: A basic implementation

This library implements the core GCRA functionality in rust.

Usage

```rust use ::gcra::{GcraState, RateLimit};

fn checkratelimit() { const LIMIT: u32 = 1; const PERIOD: Duration = Duration::fromsecs(1); // Create a rate limit that allows 5/1s let ratelimit = RateLimit::new(LIMIT, PERIOD);

let mut userstate = GcraState::default(); assert!(userstate.checkandmodify(&ratelimit, 1).isok()); assert!( !assert!(userstate.checkandmodify(&ratelimit, 1).is_err(), "We should be over the limit now" ); } ```