Added versionadded tag in docs and renamed test_inplace to test_inplace_add for consistency

Author: benthayer

doc/source/groupby.rst

@@ -126,6 +126,8 @@ We could naturally group by either the ``A`` or ``B`` columns or both:
    grouped = df.groupby('A')
    grouped = df.groupby(['A', 'B'])
 
+.. versionadded:: 0.20
+
 If we also have a MultiIndex on columns ``A`` and ``B``, we can group by all
 but the specified columns
 

pandas/tests/indexes/test_frozen.py

@@ -33,7 +33,7 @@ def test_sub_dupe(self):
         expected = FrozenList([1, 3])
         self.check_result(result, expected)
 
-    def test_inplace(self):
+    def test_inplace_add(self):
         q = r = self.container
         q += [5]
         self.check_result(q, self.lst + [5])