Merge pull request #14 from jerryneedell/jerryn_unpack

fix struct unpack issue

Author: ladyada

adafruit_bluefruitspi.py

@@ -179,7 +179,7 @@ def _cmd(self, cmd):  # pylint: disable=too-many-branches
                 spi.readinto(self._buf_rx)
 
             # Read the message envelope and contents
-            msgtype, rspid, rsplen = struct.unpack('>BHB', self._buf_rx)
+            msgtype, rspid, rsplen = struct.unpack('>BHB', self._buf_rx[0:4])
             if rsplen >= 16:
                 rsp += self._buf_rx[4:20]
             else:
@@ -242,8 +242,7 @@ def command(self, string):
                 raise RuntimeError("Error (id:{0})".format(hex(msgid)))
             if msgtype == _MSG_RESPONSE:
                 return rsp
-            else:
-                raise RuntimeError("Unknown response (id:{0})".format(hex(msgid)))
+            raise RuntimeError("Unknown response (id:{0})".format(hex(msgid)))
         except RuntimeError as error:
             raise RuntimeError("AT command failure: " + repr(error))