Use once_cell to allow for global static immutable options

So they don't have to be passed around all over the place

src/main.rs

@@ -2,13 +2,9 @@ mod listener;
 mod options;
 mod server;
 
-use structopt::StructOpt;
-
 use crate::listener::Listener;
-use crate::options::Opt;
-
 
 fn main() -> std::io::Result<()> {
-    let mut server = Listener::new(Opt::from_args())?;
+    let mut server = Listener::new()?;
     server.run()
 }