Better read/write/sizeOf interface

[rom1504]

https://github.com/Rantanen/node-dtls/blob/master/BufferBuilder.js is using a similar method than in protodef :

• a packet spec with types
• atomic reader writer by type

They are using a buffer reader and builder helpers which allow them to not care about offsets.

There might be interesting ideas in there we could use.

And it would be cool if protodef could be used in that kind of lib.

[rom1504]

https://github.com/Rantanen/node-dtls/blob/master/packets/PacketSpec.js

I think I'll try to get rid of offset, size and sizeOf throughout protodef (but keeping it sync ! No functionality change, just code improvement)

[rom1504]

Low priority, I don't want that kind of thing to slow down ProtoDef progress again.