icalendar/icalendar — pull request #82 by markrickert (2014-07-30 21:04:24+00:00)
Title: Make date and datetime sortable when using Enumberable#sort_by

Fixes issue: `comparison of Icalendar::Values::Date with Icalendar::Values::Date failed`

I was trying to do something like this:

```ruby
sorted_events = calendar.events.sort_by(&:dtstart)
```

when I got the above error. Adding these comparison methods fixes the issue.