Currently, there is no easy allocation-free way to turn a
[]byte or string into an io.Reader. Thus, we add a Reset method
to bytes.Reader and strings.Reader to allow the reuse of these
Readers with another []byte or string.
This is consistent with the fact that many standard library io.Readers
already support a Reset method of some type:
bufio.Reader
flate.Reader
gzip.Reader
zlib.Reader
debug/dwarf.LineReader
bytes.Buffer
crypto/rc4.Cipher