Add Attrs::new() test

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/obj/attrs.rs

@@ -79,8 +79,9 @@ impl Obj for Attrs {
 
 #[test]
 fn test_attrs_new() {
-    /*
-    use crate::mem::*;
-    let mut ctx = ObjCtx::new(
-    */
+    use crate::mem::BasicGc;
+
+    let mut ctx = ObjCtx::new(BasicGc::default());
+    
+    let attrs = Attrs::new(&mut ctx);
 }