Clarified in the docs how to get to the serialized bytes.

This was a frequent source of confusion, since in all implementations
the data doesn't start at offset 0 in the buffer.

Change-Id: I045966e65928e9acd9def84e215914ecb5510653

js/flatbuffers.js

@@ -238,9 +238,8 @@ flatbuffers.Builder.prototype.dataBuffer = function() {
 };
 
 /**
- * Get the ByteBuffer representing the FlatBuffer. Only call this after you've
- * called finish(). The actual data starts at the ByteBuffer's current position,
- * not necessarily at 0.
+ * Get the bytes representing the FlatBuffer. Only call this after you've
+ * called finish().
  *
  * @returns {Uint8Array}
  */