docs: changelog 5.0.2 release

Author: cwelch5

CHANGELOG.md

@@ -1,3 +1,13 @@
+<a name="5.0.2"></a>
+## [5.0.2](https://github.com/nfl/react-helmet/compare/5.0.1...v5.0.2) (2017-03-28)
+
+
+### Bug Fixes
+
+* prevent clearing existing title ([#259](https://github.com/nfl/react-helmet/issues/259)) ([549b603](https://github.com/nfl/react-helmet/commit/549b603))
+
+
+
 <a name="5.0.1"></a>
 ## [5.0.1](https://github.com/nfl/react-helmet/compare/5.0.0...v5.0.1) (2017-03-24)