add "photo_image" method to person to get the UIImage of a photo

This is related to issue #29/pull #30 where calling photo in the repl caused problems.
Returning the image is a good idea but we don't want to break existing code with a minor release (semver)
rake spec clean under RubyMotion 2.0
verified that timestamp-properties bug is not yet fixed
Merge pull request #31 from jmay/master

bug in adding contacts to groups
Added ability to get vcard for one or many AddressBook::Person object

Suggested in issue #34
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' into RM2.0