Crony: simple cron runner

Runner that will spawn a separate thread where cron jobs will be executed.

Example

```rust extern crate crony;

use crony::{Job, Runner, Schedule}; use std::str::FromStr;

struct ExampleJob; impl Job for ExampleJob { fn schedule(&self) -> Schedule { // Runs every minute Schedule::from_str("0 * * * * *").unwrap() } fn handle(&self) { println!("Hello, I am a cron job running at: {}", self.now()); } }

fn main() { println!("Hello world"); Runner::new().add(Box::new(ExampleJob)).run(); }

/* Hello world Hello, I am a cron job running at: 2020-12-10 16:01:59.740944 UTC Hello, I am a cron job running at: 2020-12-10 16:02:59.821043 UTC */ ```