Specify delay before posting a message

[Zomis]

Have the possibility to specify a delay to wait before posting a message. This might be useful to give other messages more priority. Such as the following:

• Issue label add event
• Issue label add event
• Issue label add event
• Issue opened event

In this case, issue opened event should always be the first, and then the other label events should come, and preferably be grouped together (see #12 and #13)