Make highlights stand out, re-fix empty message check, make colors seed only get set once, add "/ " as an escape for messages beginning with "/"

A clarification on the last bit: Instead of having to type "./text" or " /text" to prevent "/text" from being interpreted as a command instead of a normal message, this change allows people to prefix "/ " to messages starting with "/" to allow them to be displayed as-is. So typing "/ /text" will make it so everyone else sees "/text" in the chat.
msg will already have the color-formatted username in it even if the message the user sent was blank, where as line only contains the message they intended to send. I guess I could have done `len(line) == 0` but it's just a force of habit for me to do the other way.