Changes for Handle in Progressbar

The handle has got hover effects now: When hovering the progressbar
element, the handle will transform from a thin line up to a square.
When hovering the handle itself, it will scale up a bit.

The handle will be displayed with a correct offset value - leaving half
of the handle visible when starting or reaching the end in the progress
bar.
Changes in fonts

Change basic font-size.
Change icon-font-size from px to em.
Correct indentation
Merge pull request #193 from podlove/progressbar-handle-change

Animate scrubber on user interaction