Add in a new decoding for Blob/Buf

2bit.p6

my class 2bit does Blob[uint8] is repr('VMArray') {
    method decode(2bit:D: $encoding = '2bit') {
        die "Can not decode a 2bit buffer as if it were $encoding"
            unless $enc eq '2bit';
        #TODO the guts here
    }
    method encoding() { '2bit' }
    multi method Str(2bit:D:) { self.decode }
    multi method Stringy(2bit:D:) { self.decode }
}