Bumped pom to 2.4.0-SNAPSHOT
Notify jenkins on a separate thread to release Stash's event thread

In the worst cases Jenkins has been known to block, resulting in Stash
running out of event threads, which is Bad.
Merge branch 'notify-background-thread' of github.com:charleso/stash-jenkins-postreceive-webhook into charleso-notify-background-thread
Merge branch 'develop' into v-2.3.1

Conflicts:
	pom.xml