Awkward Method Name

Having something like `mount.mount` is extremely awkward.

Something like `on` might serve better:

``` rust
fn send_hello(req: &mut Request) -> IronResult {
Ok(Response::with(status::Ok, "Hello!"))
}

fn intercept(req: &mut Request) -> IronResult {
Ok(Response::with(status::Ok, "Blocked!"))
}

fn main() {
let mut mount = Mount::new();
mount.on("/blocked/", intercept).on("/", send_hello);

Iron::new(mount).listen(Ipv4Addr(127, 0, 0, 1), 3000);
}
```