Merge pull request #2772 from GodloveD/update-date

make the release date accurate

Author: GodloveD

CHANGELOG.md

@@ -11,7 +11,7 @@ _The old changelog can be found in the `release-2.6` branch_
 
 # Changes Since v3.1.0
 
-# v3.1.0 - [2019.02.08]
+# v3.1.0 - [2019.02.22]
 
 ## New Commands
   - Introduced the `oci` command group to support a new OCI compliant variant of the Singularity runtime: