Changes in ProtoBuf.js 2.2

Upon request the convenience methods Message#encodeDelimited([bb]) and Message.decodeDelimited(bb) have been added, which encode respectively decode a varint32 length-delimited message.

Because this is usually used to encode multiple messages into one ByteBuffer, Message.encode no longer implicitly flips the destination ByteBuffer if it is explicitly specified:

var MyMessage = builder.build("MyMessage");
var myMessage = new MyMessage(...);

// If omitted, nothing has changed:
var bb = myMessage.encode(); // 2.0: flips, 2.2: flips

// If explicitly specified, it does not flip anymore so that
// multiple messages can easily be written into one ByteBuffer:
var bb = new ByteBuffer();
myMessage.encode[Delimited](bb); // 2.0: flips: 2.2: does not flip