[doc] update CHANGELOG + document support for numeric literals

CHANGELOG

@@ -13,6 +13,7 @@ Python 3 parsing:
 - support ellipsis https://github.com/PyCQA/baron/pull/121 by odcinek
 - support matrix operator https://github.com/PyCQA/baron/pull/117 by odcinek
 - support f-strings https://github.com/PyCQA/baron/pull/110 by odcinek
+- support numeric literals https://github.com/PyCQA/baron/pull/111 by odcinek
 0.6.6 (2017-06-12)
 ------------------

docs/grammar.rst

@@ -107,6 +107,18 @@ RedBaron: TODO
     add f'' rf'' fr'' to the lexer
+Underscore in numeric literals
+------------------------------
+
+Python 3.6
+
+Baron: https://github.com/PyCQA/baron/pull/111
+RedBaron: probably nothing to do (to be confirmed)
+
+::
+
+    modify lexer to handle this
+
 TODO
 ====