Class for person divs / image span

[ChrisRackauckas]

One thing I noticed when reviewing Tao's latest PR is the following:

https://github.com/Tao2012/nielab.github.io/blob/adb3d6f436b547adda628b8d7cc1eb99704c9aaf/people/tao-peng.html#L23

That div is pretty specific: that setup should be implemented as a CSS class and then the div should just be set to that class. Instead of wrapping the image in a span and then setting the width, it should just be a class itself which sets the image left class and adds the width.

These are very non-essential though.