Sidebar design improvements

[unwitting]

With the new square logo it's easy to run out of vertical space on the sidebar - some ideas:

• Different fixed-aspect logo (2:1?)
• Slimmer sidebar items?
• Vertical scroll in the case that it overflows

[THS-on]

I have a lot of links in my sidebar, so vertical scroll is for me the easiest solution. Other ideas:

• Auto scale sidebar
• Switch to mobile theme