title: What does "^" mean in package.json versioning?
body: <p>I recently ran <code>npm install</code> (npm 1.4.3) with the <code>--save-dev</code> flag and the package entries it added to my package.json all began with a <code>^</code>, e.g. <code>"^2.5.0"</code>. I have never seen this before with the earlier versions of npm I have used, and I cannot find any documentation for this notation, only for the notations I'm already familiar with, e.g. <code>~</code>, <code>&gt;=</code> etc.. What does it mean?</p>