Hello!
Thanks a lot for your awesome lib!
We're currently using it for a big work on a vcf vcard manager on nextcloud.

Recently, I noticed that the _designSet.property on vcard version 4.0 is the same than the vcard 3.0. I tried with 2 different vcards from the rfc files (so should not have any issues here)

JsFiddle: http://jsfiddle.net/227efboL/2260/
You can see that both of the design sets are 35 length, but the designset for v3 should be 28.

@mschroeder @kewisch