Merge pull request firebase#483 from firebase/schmidt-sebastian-patch-2

Updating CHANGELOG for Storage to 2.1.0

Author: schmidt-sebastian

Firebase/Storage/CHANGELOG.md

@@ -1,3 +1,6 @@
+# v2.1.0
+- [added] Added 'md5Hash' to FIRStorageMetadata.
+
 # v2.0.2
 - [changed] Custom FIRStorageMetadata can now be cleared by setting individual properties to 'nil'.