Correct bumpversion search/replace for CHANGELOG

The # in Markdown gets treated as a comment so there is no way to
do multiline search/replace. As a result only a single line with
the version number is replaced. The # Latest headline will have to
be added manually on the next set of changes.

See peritus/bumpversion#199

setup.cfg

@@ -13,12 +13,8 @@ search = __version__ = "{current_version}"
 replace = __version__ = "{new_version}"
 
 [bumpversion:file:CHANGELOG.md]
-search =
-    # Latest
-replace =
-    # Latest
-
-    # {new_version} ({now:%%Y-%%m-%%d})
+search = ## Latest
+replace = ## {new_version} ({now:%%Y-%%m-%%d})
 
 [bumpversion:file:setup.py]
 search = version="{current_version}"