Remove BaseObj and fix Object::equals

* BaseObj felt a bit redundant. For everything that BaseObj did, we use
  Obj instead.
* Object::equals was a little weird. It was used for giving back
  equality, except when it wasn't. It's a little better defined now,
  here's what I'm shooting for:
    * *In general*, Object::equals will return true when two objects
      refer to the same object.
    * The exception to this rule is for "constant" objects, or "copy on
      write" objects. These include, but are not limited to: Int, Float,
      Bool, Nil, Str. Their base values are immutable and are the heart
      of object equality.

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

src/obj/module.rs

@@ -5,12 +5,12 @@ use gc::{Finalize, Trace};
 
 use crate::obj::macros::*;
 use crate::obj::prelude::*;
-use crate::obj::BaseObj;
+use crate::obj::Obj;
 use crate::vm::Chunk;
 
 #[derive(Trace, Finalize)]
 pub struct Module {
-    base: BaseObj,
+    base: Obj,
     #[unsafe_ignore_trace]
     path: Rc<String>,
     #[unsafe_ignore_trace]
@@ -66,15 +66,6 @@ impl Display for Module {
 }
 
 impl Object for Module {
-    fn equals(&self, other: &dyn Object) -> bool {
-        if let Some(other) = other.as_any().downcast_ref::<Module>() {
-            // only referential identity
-            std::ptr::addr_eq(self, other)
-        } else {
-            false
-        }
-    }
-
     impl_base_obj!(Module);
 }