HTML injection vulnerability

[sparksis]

Users with a name similar to <span>Name can maliciously inject HTML into the page causing undesired effects (Or in the case of my users who figured it out change their color harmlessly).

Please review: http://docs.mybb.com/1.8/development/standards/#sanitizing-data-for-output and sanitize any data that is not well defined by steam (Name/game (depends on if non steam games are passed through)). Typically I'd submit this as a pull request but I'm not as familiar with PHP.

Thanks,