icalendar/icalendar — pull request #98 by jeremyevans (2014-10-22 17:32:59+00:00)
Title: Use more specific check for ActiveSupport timezone support

Just checking for ActiveSupport isn't enough. Some libraries
define the top level ActiveSupport module, that doesn't mean
that the classes you need to use exist.

See https://github.com/mikel/mail/pull/816 for an example,
where loading icalendar and mail without activesupport being
installed results in a broken icalendar.