Percent encode (url encode) a Sequence of bytes, as specified in RFC 3986 section 2.1

* Bytes values of a save (unreserved) character (A-Z, a-z, 0-9, "-", ".", "_" and "~") are encoded as that character.
* All other values are encoded as "%HH", where HH is the hexadecimal representation of the byte, using uppercase letters