title: Set minimum width of new vertical split in Vim
body: <p>I have my Vim window set to 90 columns using <code>set columns=90</code>, but this causes problems when commands (<code>pyunit-vim</code>, in particular) open new vertical splits, because each window then only has 45 columns, which is far too narrow. Ideally, I'd like to add splits to the existing width, rather than impinge upon it. Is there some way to specify this behaviour?</p>