Update CHANGELOG.md for 8.15.1

[ci skip]

CHANGELOG.md

@@ -2,6 +2,16 @@
 documentation](doc/development/changelog.md) for instructions on adding your own
 entry.
+## 8.15.1 (2016-12-23)
+
+- Push payloads schedule at most 100 commits, instead of all commits.
+- Fix Mattermost command creation by specifying username.
+- Do not override incoming webhook for mattermost and slack.
+- Adds background color for disabled state to merge when succeeds dropdown. !8222
+- Standardises font-size for titles in Issues, Merge Requests and Merge Request widget. !8235
+- Fix Pipeline builds list blank on MR. !8255
+- Do not show retried builds in pipeline stage dropdown. !8260
+
 ## 8.15.0 (2016-12-22)
 - Whitelist next project names: notes, services.

changelogs/unreleased/25905-mr-when-succeeds-dropdown.yml

----
-title: Adds background color for disabled state to merge when succeeds dropdown
-merge_request: 8222
-author:

changelogs/unreleased/25906-title-size.yml

----
-title: Standardises font-size for titles in Issues, Merge Requests and Merge Request widget
-merge_request: 8235
-author:

changelogs/unreleased/25961-spec-list-blank.yml

----
-title: Fix Pipeline builds list blank on MR
-merge_request: 8255
-author:

changelogs/unreleased/fix-hide-retried-builds-in-pipeline-stage-dropdown.yml

----
-title: Do not show retried builds in pipeline stage dropdown
-merge_request: 8260
-author:

changelogs/unreleased/fix-mattermost-username.yml

----
-title: Fix Mattermost command creation by specifying username
-merge_request:
-author:

changelogs/unreleased/issue_25887.yml

----
-title: Do not override incoming webhook for mattermost and slack
-merge_request:
-author:

changelogs/unreleased/process-commit-worker-large-batches.yml

----
-title: Push payloads schedule at most 100 commits, instead of all commits
-merge_request:
-author: