Responsive to half-width and narrow layouts
On my 13" Macbook Pro, I like to have two applications up side-by-side. However, Airmail's layout is too wide to fit within half my screen. Make Airmail's layout more responsive so that we can resize it to 600px wide or less.
(Exactly half-screen width is important for use with window management applications like Magnet, Divvy, Window Keys, Optimal Layout, and BetterSnapTool.