liuggio/ExcelBundle — pull request #42 by lemoinem (2013-06-20 19:44:30+00:00)
Title: Swtich "CodePlex/PHPExcel" required version to 1.7.9 (last stable)

It's the last stable release. Plus, as mentioned on https://phpexcel.codeplex.com/ it's the last stable before 2.0.0

So I think it would be a great idea to upgrade the current required version and then watch out for 2.0.0...