Ianjorgensen/message image tag

This is the icon on notes project i worked on the hackathon, i want to code to be there so when we have icons we can use we can simply add the regex's and it will all just work. cc @jebeck  @nicolashery 
You are saying you want the messageImageTags to come from the main react component? @jebeck. I'd be happy to do that. I'll also remove the image icon. I want to get it merged so that if Howard and Brandon decide to use it its there. Thank you for looking into it.