removed xAsDataframe
updated docs
added medianby
updated test predicates
strengthened more tests
added failing test for riffle
updated tests
added predicate for na's in list, fixing test
refactoring testing tool
refactored test to use unit test label
added an integration test
added missing dependency
removed broken test stub
updated more tests
updated tests
Updated docs
updated docs
updated tests
updated to use r type
updated several tests and examples