clearly describe encap/decap algorithm

[thomas-fossati]

In order to avoid misunderstandings, it'd be beneficial to describe the encap/decap algorithms in a more explicit manner

[thomas-fossati]

Maybe add this bit from the TCG spec:

A parser decodes the octet string into a byte buffer
and then does a 1-byte lookahead, as illustrated in the
following pseudo code, to decide which format to use to
decode the remainder of the byte buffer:

switch b[0] {
case 0x82:
  return CBORArray
case 0x5b:
  return JSONArray
default:
  return CBORTag
}