test_fromfile - add the custom convert_arg_line_to_args test

argcoffee - explore alt codings of args_from_files
    using forEach (as would be used in the JS code)
    using asysc readfile - that does not work

test_filetype - test of the FileType action.type
    It sets the namespace value to either a process.stdin object or
     a file's handle (fd).  That's not terribly useful
     Only advantage to a FileType is it lets argparse handle the
     error messages.

test_types - explore a custom action.type, such as a Date.
     It works with both argparse and argcoffee
     however there are differences in error messages
     argparse copies py. for builtin types, but shows the
     action.type.toString() rather than its name (__name__)
     argcoffee just passes on the error message from action.type
     A compromise that passes on the type message might be worth suggesting