Added unit tests for packets.

Also did some code cleanup.

examples/plugins/example_plugin.py

@@ -2,18 +2,18 @@ import logging
 
 from aprsd import packets, plugin
 
-LOG = logging.getLogger("APRSD")
+LOG = logging.getLogger('APRSD')
 
 
 class HelloPlugin(plugin.APRSDRegexCommandPluginBase):
     """Hello World."""
 
-    version = "1.0"
+    version = '1.0'
     # matches any string starting with h or H
-    command_regex = "^[hH]"
-    command_name = "hello"
+    command_regex = '^[hH]'
+    command_name = 'hello'
 
     def process(self, packet: packets.MessagePacket):
-        LOG.info("HelloPlugin")
+        LOG.info('HelloPlugin')
         reply = f"Hello '{packet.from_call}'"
         return reply