[timeline/recent-activity] Update the recent activity, per Issue #25.
[timeline/only-me-border] Style the "Only Me" border. Stop using -webkit-linear-gradient.

The reason is that modern browsers now supports linear gradients
natively. It will work on Firefox 16, Chrome 26, IE 10.

https://developer.mozilla.org/en-US/docs/Web/CSS/linear-gradient
[timeline/show-more] Style the show more button in the timeline.
[timeline/composer, timeline/section-header] Style the section header (Issue #25) and timeline composer (closes #22).