Fix the invalid restructured text in HISTORY file
This was breaking the display of our long_description on PyPI.
@@ -52,8 +52,8 @@ dev
**Bugfixes**
-- Fix an error in the packaging whereby the *.whl contained incorrect data that
- regressed the fix in v2.17.3.
+- Fix an error in the packaging whereby the ``*.whl`` contained incorrect data
+ that regressed the fix in v2.17.3.
2.18.0 (2017-06-14)
+++++++++++++++++++
