Async User Lookup

An easy way to lookup Linux/Unix user and group information from /etc/passwd and /etc/group. It uses tokio async and will cache the information for a duration specified by the user.

```rust use asyncuserlookup::PasswdReader; use std::time::Duration;

[tokio::main]

async fn main() { let mut reader = PasswdReader::new(Duration::new(0,0));

println!("User with uid 1000 is: {}", reader.getusernameby_uid(1000).await.unwrap().unwrap()); }

```