Setting @message.sender_ip

I noticed when APP_TRACK_IP was set to true that every new message creation would come back with: 

>"Oops! You forgot to give me something to protect."

I tracked down the problem to the model class, where I saw it was failing to set the sender_ip instance variable, which seems to be because models don't have any notion of web request information unless you pass it to them. I fixed it by setting the sender_ip value in the controller (cheap and cheerful).