HAWelcome Hooked to a different event.

HAWelcome's job scheduling and all relevant checks are now done later,
on ArticleSaveComplete. Previously the process was hooked to the
RevisionInsertComplete, but it turned out the event happens after
the user's local edit count is increased after an edit.
Oops.
Merge pull request #937 from Wikia/dev-CE-39-hawelcome-intermittent-double-welcomes

HAWelcome Hooked to a different event.