Improve replace on HyObject so it does less work

Calling `replace` can trigger a call to `replace_hy_obj`, which will
try to also wrap values inside a `HyObject`.

However, this means when we try to recusively replace inside a nested
object, like a `HyList`, we should try and capture these new wrapped
objects.

Hy still works if we don't, but it results in the object getting
rewrapped multiple times during a compile.

Closes hylang#1519

hy/models.py

@@ -226,11 +226,8 @@ class HyList(HyObject, list):
     """
 
     def replace(self, other):
-        for x in self:
-            replace_hy_obj(x, other)
-
-        HyObject.replace(self, other)
-        return self
+        self[:] = [replace_hy_obj(x, other) for x in self]
+        return HyObject.replace(self, other)
 
     def __add__(self, other):
         return self.__class__(super(HyList, self).__add__(other))
@@ -391,7 +388,7 @@ def replace(self, other):
         if self.cdr is not None:
             replace_hy_obj(self.cdr, other)
 
-        HyObject.replace(self, other)
+        return HyObject.replace(self, other)
 
     def __repr__(self):
         if PRETTY: