added tests for CKIFile, CKIService, CKIQuiz and CKIGroup
Merge remote-tracking branch 'upstream/master'
Merge pull request #131 from elgreco84/master

Added more tests
added swift tests for following models:

CKIExternalTool
CKIDiscussionTopic
CKIActivityStreamMessageItem
CKIActivityStreamItem
CKIActivityStreamDiscussionTopicItem
CKIActivitySTreamConversationItem