Housekeeping: Changed Behat sentences for clarity.
Implemented: Motivating feature for frequent item set analysis. Refs. #29
Implemented: Sentence to create a fake change analysis result.
Updated: Frequent item set feature with minimum support. Refs. #29
Implemented: Set class. Refs. #29
Implemented: Further set operations. Refs. #29
Implemented: More convenience methods for Set class. Refs. #29
Implemented: MutableSet class. Refs. #29
Implemented: FrequentItemSet class. Refs. #29
Implemented: Initial version of Frequent Item Set analysis. Refs. #29