comment out most part of Design.init
fix BitVector#self_op for inv and inv! methods
eliminate eval in BitVector#to_i
fix BitVector(n) with negative int
add require path in Bit.rb testcode
BitVector#^, BitVector#& should be bin_arg_ops
test_or pattern should not be '1111'
comment out String#bin, altered by to_i(2). Fixnum#inv should be round-tripping, now defined by ~self
remove working? file examples/tmp