Convert the Serial.Println to string
Those numbers are the numerical ASCII representation of the characters.

83 = S
101 = e
110 = n
... etc ...


(Find the whole list here: http://www.asciitable.com/)

The reason you are ending up with numbers is because of the type of variable you are receiving the data into - a byte.

A byte stores a number between 0 and 255.  When you add that byte to a String the compiler assumes you want to append a number, since it is a numerical type that you are using.

If you instead tell it to use a char type then the compiler should realise "Ah, this is the numeric representation of a character - I will add the character instead".

You can either change the whole array type:

char message[VW_MAX_MESSAGE_LEN]; // a buffer to store the incoming messages


Or cast the variable to be the right type when you append it:

  sensorname += (char)message[i];


Or better still, don't use the String class since it is really too heavyweight and prone to memory issues for use on a little microcontroller.  Stick to C strings. They take a little more getting used to, but are so much more microcontroller friendly.