Fix incorrect order of commit message in Safari

Fixes #226.

Per https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort, sort functions should return less than zero, zero, or greater than zero to determine the sort order, not a boolean value. We were getting away with this in Chrome and Firefox but it seems like newer versions of Safari are stricter on this.

Tested:
* Safari 7.0.6
* Chrome 37.0.2062.94
* Firefox 31.0

All on OS X 10.9.4.