Use default rust directory structure for tests

tests/comments.rs

@@ -0,0 +1,12 @@
+extern crate rhai;
+
+use rhai::Engine;
+
+#[test]
+fn test_comments() {
+	let mut engine = Engine::new();
+
+	assert!(engine.eval::<i64>("let x = 5; x // I am a single line comment, yay!").is_ok());
+
+	assert!(engine.eval::<i64>("let /* I am a multiline comment, yay! */ x = 5; x").is_ok());
+}