Run completions for your program
# Example
```rust,no_run
# #[cfg(unix)] {
# use std::path::Path;
# let bin_root = Path::new("").to_owned();
# let completion_script = "";
# let home = std::env::current_dir().unwrap();
let term = completest_pty::Term::new();
let mut runtime = completest_pty::BashRuntime::new(bin_root, home).unwrap();
runtime.register("foo", completion_script).unwrap();
let output = runtime.complete("foo \t\t", &term).unwrap();
# }
```