PostToSlack - Posts a message to a slack-channel

Usage: posttoslack CHANNEL/A,USERNAME/A,MESSAGE/A

CHANNEL: The Slack-channelname to post the message to
USERNAME: The username which the message will be posted under
MESSAGE: The message

This script also needs the ENV-variable SLACKAPIKEY to be set, the key can
be recieved from slack and is set using:

SetENV SLACKAPIKEY "xxxxxxxxx/xxxxxxxxx/xxxxxxxxxxxxxxxxxxxxxxx"