It was initially added to allow reuse of aruba cucumber steps, using
`must' instead of `should'. This is creating more harm than good, hence
we remove it and implements all missing steps, using aruba API.
Cucumber chomp the last \n from multiline strings (docstrings), this
monkey patch modify Cucumber::Ast::DocString constructor to add the
missing ending new line character and
Cucumber::Formatter::Pretty#doc_string to remove it from the output.
