Document commit change notifications
Change notifer commit change environment variables

DELIVER_CHANGES     -> HEAVEN_NOTIFIER_DISPLAY_COMMITS
COMMIT_CHANGE_LIMIT -> HEAVEN_NOTIFIER_DISPLAY_COMMITS_LIMIT
Merge pull request #114 from dblandin/update-commit-change-environment-variables

Change notifer commit change environment variables
Merge pull request #109 from dblandin/document-commit-changes

Document commit change notifications
Don't use the top-level keys, use newer nested ones
Merge pull request #120 from ZeroFucks/top-level-payload-keys

Don't use the top-level keys, use newer nested ones
Merge branch 'master' of https://github.com/atmos/heaven