Implement a ofType filter for filtering items of a specified type
User isKindOfClass instead of isSubclassOfClass and use where: method instead of enumerating
Add ofType
Merge pull request #4 from jacksonh/ofType

Implement a ofType filter for filtering items of a specified type
Merge pull request #5 from jacksonh/sequenceEqual

Implement a sequenceEqual method for comparing two sequences