Add a minimal single-threaded example.

tests/minimal.rs

@@ -0,0 +1,12 @@
+extern crate ralloc;
+
+#[test]
+fn minimal() {
+    let mut a = Box::new(1);
+    let mut b = Box::new(2);
+    let mut c = Box::new(3);
+
+    assert_eq!(*a, 1);
+    assert_eq!(*b, 2);
+    assert_eq!(*c, 3);
+}