Update changelog for 2.8.0 release (#2119)

Author: amrocha

CHANGELOG.md

@@ -8,6 +8,21 @@ The format is based on [these versioning and changelog guidelines](https://git.i
 
 ---
 
+## 2.8.0 - 2018-08-30
+
+### Bug fixes
+
+- Reverted a change that caused the built embeded.js bundle to be way larger than it should be due to broad imports ([#2102](https://github.com/Shopify/polaris-react/pull/2102))
+
+### Enhancements
+
+- Added support for boolean type on Choice error prop ([#2085](https://github.com/shopify/polaris-react/pull/2085))
+
+### Documentation
+
+- Updated banner guidelines to make it clearer when success banners should be used vs success toasts. ([#2046](https://github.com/Shopify/polaris-react/pull/2046))
+- Updated display text documentation to have a separate example for medium and large display ([#2100](https://github.com/Shopify/polaris-react/pull/2100))
+
 ## 2.7.2 - 2018-08-27
 
 ### Bug fixes

UNRELEASED.md

@@ -3,16 +3,3 @@
 Use [the changelog guidelines](https://git.io/polaris-changelog-guidelines) to format new entries. 💜
 
 ---
-
-### Bug fixes
-
-- Reverted a change that caused the built embeded.js bundle to be way larger than it should be due to broad imports ([#2102](https://github.com/Shopify/polaris-react/pull/2102))
-
-### Enhancements
-
-- Added support for boolean type on Choice error prop ([#2085](https://github.com/shopify/polaris-react/pull/2085))
-
-### Documentation
-
-- Updated banner guidelines to make it clearer when success banners should be used vs success toasts. ([#2046](https://github.com/Shopify/polaris-react/pull/2046))
-- Updated display text documentation to have a separate example for medium and large display