Use div tags instead of P, for BBcode compatibility

Because BBCodes may introduce div tags and other tags not valid inside of P tags, we should replace the use of P tags with DIV tags instead for the output of the message content..
Basically it is to make our preview look as close as possible as to what it looks like on the board, and to prevent any issues that may arise from the possible BBCodes people may try to use (that's what the overflow is for).