Update VERSION in CalendarHelper to match 0.2.6.

Gemspec is updated to 0.2.6, but this reference in CalendarHelper wasn't updated: https://github.com/topfunky/calendar_helper/blob/b7b91b49e0c586e96fa2022e88756c632b65a8a6/calendar_helper.gemspec#L5

I don't know what it's being used for, but it was pretty confusing to debug another issue with this fake version number.