feat(icons): Mixing, editing, mastering, etc.
style(icons): Remove buttons, link with icons

I thought the buttons were overkill, so I replaced them with links in
the actual icons themselves. I left this separate since it may not be
immediately clear that there's a link there. Perhaps it needs to be more
obvious that the icons are clickable?
Merge pull request #4 from emergencesound/new-icons

New icons