Don't scroll down while I'm reading up

[MadaraUchiha]

Right now, when someone posts a message it would automatically scroll down to the bottom of the page. That makes it impossible to read up the transcript.

Scroll should only happen if I'm already at the bottom of the page when the message gets issued.

[Canop]

Done : 99c5948

Code is a little too heavy for my taste but it should work ('twas painful to deal with the padding...).