'Places data at the front of the buffer.
Arguments:
data(str,Buffer): Data to place at the beginning of the buffer.
Example:
>>> b = Buffer()
>>> b.add("hello")
>>> b.add("world")
>>> b.get(5)
\'hello\'
>>> b.unget("goodbye")
>>> b.get()
\'goodbyeworld\''

def unget(self, data):

    if isinstance(data, Buffer):
        self.data = (data.data + self.data)
        self.size += data.size
    else:
        self.data.insert(0, data)
        self.size += len(data)
