Check if stdin is from a tty

src/lib.rs

-#[test]
-fn it_works() {
+#![feature(libc)]
+extern crate libc;
+
+pub fn readline() -> Option<String> {
+    // Buffer to hold readline input
+    let buffer = String::new();
+
+    let isatty = unsafe { libc::isatty(libc::STDIN_FILENO as i32) } != 0; 
+    if isatty  {
+        println!("stdin is a tty");
+    } else {
+        println!("stdin is not a tty");
+    }
+
+    buffer
 }