Moving into rustbook namespace

rustbook/guessing_game/src/main.rs

@@ -0,0 +1,14 @@
+use std::io;
+
+fn main() {
+    println!("Guess the number!");
+
+    println!("Please input your guess.");
+
+    let mut guess = String::new();
+
+    io::stdin().read_line(&mut guess)
+        .expect("Failed to read line");
+
+    println!("You guessed: {}", guess);
+}