Improve type definitions for decode about rlp

[wemeetagain]

An additional wrinkle, the readme says :
rlp.decode(encoded, [skipRemainderCheck=false]) - Decodes an RLP encoded Buffer, Array or String and returns a Buffer or an Array of Buffers. If skipRemainderCheck is enabled, rlp will just decode the first rlp sequence in the buffer. By default, it would throw an error if there are more bytes in Buffer than used by rlp sequence.

It looks like the skipRemainderCheck logic is gone.

EDIT:
the skipRemainderCheck param isn't needed anymore because the stream param does the same thing and more.