Update CHANGELOG.md for 8.15.4

[ci skip]

CHANGELOG.md

@@ -2,6 +2,16 @@
 documentation](doc/development/changelog.md) for instructions on adding your own
 entry.
 
+## 8.15.4 (2017-01-09)
+
+- Make successful pipeline emails off for watchers. !8176
+- Speed up group milestone index by passing group_id to IssuesFinder. !8363
+- Don't instrument 405 Grape calls. !8445
+- Update the gitlab-markup gem to the version 1.5.1. !8509
+- Updated Turbolinks to mitigate potential XSS attacks.
+- Re-order update steps in the 8.14 -> 8.15 upgrade guide.
+- Re-add Google Cloud Storage as a backup strategy.
+
 ## 8.15.3 (2017-01-06)
 
 - Rename wiki_events to wiki_page_events in project hooks API to avoid errors. !0 (8425)

changelogs/unreleased/26014-fix-update-doc.yml

----
-title: Re-order update steps in the 8.14 -> 8.15 upgrade guide
-merge_request:
-author:

changelogs/unreleased/26051-fix-missing-endpoint-route-method.yml

----
-title: Don't instrument 405 Grape calls
-merge_request: 8445
-author:

changelogs/unreleased/patch-turbolinks.yml

----
-title: Updated Turbolinks to mitigate potential XSS attacks
-merge_request:
-author:

changelogs/unreleased/remove-successful-pipeline-emails-for-now.yml

----
-title: Make successful pipeline emails off for watchers
-merge_request: 8176
-author:

changelogs/unreleased/speed-up-group-milestone-index.yml

----
-title: Speed up group milestone index by passing group_id to IssuesFinder
-merge_request: 8363
-author:

changelogs/unreleased/support-google-cloud-storage-backups.yml

----
-title: Re-add Google Cloud Storage as a backup strategy
-merge_request:
-author:

changelogs/unreleased/update-gitlab-markup-gem.yml

----
-title: Update the gitlab-markup gem to the version 1.5.1
-merge_request: 8509
-author: