chore: changelog

CHANGELOG.md

+<a name="0.5.0"></a>
+# [0.5.0](https://github.com/vuejs/vuepress/compare/v0.4.2...v0.5.0) (2018-04-16)
+
+
+### Features
+
+* dropdown Items in Navbar ([#13](https://github.com/vuejs/vuepress/issues/13)) ([79f8f14](https://github.com/vuejs/vuepress/commit/79f8f14))
+* enhanceApp.js ([#80](https://github.com/vuejs/vuepress/issues/80)) ([37ea038](https://github.com/vuejs/vuepress/commit/37ea038))
+* support adding custom page class in front matter ([#85](https://github.com/vuejs/vuepress/issues/85)) ([40ca73c](https://github.com/vuejs/vuepress/commit/40ca73c)), closes [#84](https://github.com/vuejs/vuepress/issues/84)
+
+
+
 <a name="0.4.2"></a>
 ## [0.4.2](https://github.com/vuejs/vuepress/compare/v0.4.1...v0.4.2) (2018-04-16)