ruby: reindent everything to 4 spaces.. what was i thinking with 8 spaces
ruby: bump sereal protocol version of the encoder
ruby: buffered stream read

improve performance by simply using local
buffer to reduce the number of read() syscalls

time took to decode 1_000_000 times:
obj = {
  "name" => "jack doe",
  "quantity" => 1_000_000,
  "some_unicode" => {
     "Chinese (汉语 or 漢語, Hànyǔ)" => [ 1,2,3,4,5 ]
  }
}

          user     system      total        real
Sereal   4.800000   0.670000   5.470000 (  5.510288)
MsgPack  3.630000   0.650000   4.280000 (  4.319019)

there is still place for improvement,
but this is around 10* what it took without
buffering the read()s
ruby: add readme about the streaming support