Add testframework/Test.roc

[jxxcarlson]

This PR adds interface Test.roc:

# This interface provides a simple way to run tests.  A test is a record
# with two fields:
#
#     Test : { name : Str, test: Bool }
#
# for example,
#
#     t1 = {name : "1 + 1 == 2", test: 1 + 1 == 2}
#
# You run tests like this:
#
#     [t1,t2] |> Test.run "Test of potrezebie interface"  |> Task.putLine
#
# or 
#
#     [t1,t2] |> Test.runF "Test of potrezebie interface"  |> Task.putLine
#
# if you want to see failures only.
#