Fix changelog Markdown syntax

CHANGELOG.md

@@ -2,7 +2,8 @@
 
 <!-- ## [Unreleased] -->
 
-## [5.1.0] - 2018-07-5
+## [5.1.0] - 2018-07-05
+
 - Added a new custom rule `plugin/content-no-strings` that disallows hard-coded strings as values for the `content` property. This prevents internationalization issues. Keywords are still allowed.
 
 The following patterns are considered violations:
@@ -25,9 +26,6 @@ The following patterns are _not_ considered violations:
 .foo::before { content: open-quote counter(section_counter) close-quote; }
 ```
 
-
-
-
 ## [5.0.1] - 2018-04-06
 
 - Updated dependency: stylelint-css (no breaking changes, only fixes)
@@ -170,7 +168,8 @@ property: <top> <right> <bottom> <left>
 * Initial release
 
 
-[Unreleased]: https://github.com/Shopify/stylelint-config-shopify/compare/v5.0.1...HEAD
+[Unreleased]: https://github.com/Shopify/stylelint-config-shopify/compare/v5.1.0...HEAD
+[5.1.0]: https://github.com/Shopify/stylelint-config-shopify/compare/v5.0.1...v5.1.0
 [5.0.1]: https://github.com/Shopify/stylelint-config-shopify/compare/v5.0.0...v5.0.1
 [5.0.0]: https://github.com/Shopify/stylelint-config-shopify/compare/v4.0.0...v5.0.0
 [4.0.0]: https://github.com/Shopify/stylelint-config-shopify/compare/v3.0.2...v4.0.0