Mostly TODO.
For many usages stream positions are irrelevant. However one should pay attention to them when devising readers and writers so that errors are reported accurately.
Byte reader and writers maintain a stream position which is the zero-based index of the next byte to read or write. This value can also be intepreted as the number of bytes that have been read or written.
The conventions are described in Bytesrw.Bytes.Reader.filter
Explain the behaviour about Bytesrw.Bytes.Slice.eod. The conventions are described in Bytesrw.Bytes.Writer.filter