docs: add changelog for 5.1.1

Author: jasonaden

CHANGELOG.md

@@ -1,3 +1,22 @@
+<a name="5.1.1"></a>
+## [5.1.1](https://github.com/angular/angular/compare/5.1.0...5.1.1) (2017-12-13)
+
+
+### Bug Fixes
+
+* **animations:** ensure multi-level route leave animations are queryable ([#20787](https://github.com/angular/angular/issues/20787)) ([d09d497](https://github.com/angular/angular/commit/d09d497)), closes [#19807](https://github.com/angular/angular/issues/19807)
+* **animations:** ensure the web-animations driver properly handles empty keyframes ([#20648](https://github.com/angular/angular/issues/20648)) ([c3e8731](https://github.com/angular/angular/commit/c3e8731)), closes [#15858](https://github.com/angular/angular/issues/15858)
+* **animations:** properly recover and cleanup DOM when CD failures occur ([#20719](https://github.com/angular/angular/issues/20719)) ([e6a2805](https://github.com/angular/angular/commit/e6a2805)), closes [#19093](https://github.com/angular/angular/issues/19093)
+* **animations:** support webkit-based vendor prefixes for prop validations ([#19055](https://github.com/angular/angular/issues/19055)) ([501f01e](https://github.com/angular/angular/commit/501f01e)), closes [#18921](https://github.com/angular/angular/issues/18921)
+* **bazel:** don't equate moduleName with fileName ([#20895](https://github.com/angular/angular/issues/20895)) ([0c9f7b0](https://github.com/angular/angular/commit/0c9f7b0))
+* **compiler:** support referencing enums in namespaces ([#20947](https://github.com/angular/angular/issues/20947)) ([d6da798](https://github.com/angular/angular/commit/d6da798)), closes [#18170](https://github.com/angular/angular/issues/18170)
+* **compiler-cli:** disable checkTypes in emit. ([#20828](https://github.com/angular/angular/issues/20828)) ([160a154](https://github.com/angular/angular/commit/160a154))
+* **compiler-cli:** fix swallowed Error messages ([#20846](https://github.com/angular/angular/issues/20846)) ([6727336](https://github.com/angular/angular/commit/6727336))
+* **compiler-cli:** merge [@fileoverview](https://github.com/fileoverview) comments. ([#20870](https://github.com/angular/angular/issues/20870)) ([be9a737](https://github.com/angular/angular/commit/be9a737))
+* **router:** NavigatonError and NavigationCancel should be emitted after resetting the URL ([#20803](https://github.com/angular/angular/issues/20803)) ([baeec4d](https://github.com/angular/angular/commit/baeec4d))
+
+
+
 <a name="5.1.0"></a>
 # [5.1.0](https://github.com/angular/angular/compare/5.1.0-rc.1...5.1.0) (2017-12-06)