Get rid of move_to_end

Instead, just set a placeholder sequence_number

Fixes adafruit#18

Author: tannewt

adafruit_ble_broadcastnet.py

@@ -149,10 +149,10 @@ class AdafruitSensorMeasurement(Advertisement):
     """Battery voltage in millivolts. Saves two bytes over voltage and is more readable in bare
        packets."""
 
-    def __init__(self, *, sequence_number=None):
+    def __init__(self, *, sequence_number=0):
         super().__init__()
-        if sequence_number:
-            self.sequence_number = sequence_number
+        # Always set the sequence number so that it's always first in the packet
+        self.sequence_number = sequence_number
 
     def __str__(self):
         parts = []
@@ -164,13 +164,6 @@ def __str__(self):
                     parts.append("{}={}".format(attr, str(value)))
         return "<{} {} >".format(self.__class__.__name__, " ".join(parts))
 
-    def __bytes__(self):
-        """The raw packet bytes."""
-        # Must reorder the ManufacturerData contents so the sequence number field is always first.
-        # Necessary to ensure that match_prefixes works right to reconstruct on the receiver.
-        self.data_dict[255].data.move_to_end(3, last=False)
-        return super().__bytes__()
-
     def split(self, max_packet_size=31):
         """Split the measurement into multiple measurements with the given max_packet_size. Yields
         each submeasurement."""