Add some docstrings

diff --git a/zeroconf.py b/zeroconf.py
index 3c23033..94eafaa 100644
--- a/zeroconf.py
+++ b/zeroconf.py
@@ -51,6 +51,7 @@ class ZeroconfThread(threading.Thread):
         return True

     def _interface_for_type(self,type):
+        "Return Dbus interface to Avahi for given service type"
         return dbus.Interface(self.bus.get_object(avahi.DBUS_NAME,
                 self.server.ServiceBrowserNew(avahi.IF_UNSPEC,
                         avahi.PROTO_UNSPEC,
@@ -58,10 +59,13 @@ class ZeroconfThread(threading.Thread):
                 avahi.DBUS_INTERFACE_SERVICE_BROWSER)

     def _avahi_connect(self):
+        "Connect to Avahi via Dbus"
         self.bus = dbus.SystemBus()
         self.server = dbus.Interface(self.bus.get_object(avahi.DBUS_NAME, avahi.DBUS_PATH_SERVER),avahi.DBUS_INTERFACE_SERVER)

     def _service_type(self):
+        "Return zeroconf service type, dependent on master/relay mode"
+
         if self.master:
             t = 'master'
         else:
@@ -69,6 +73,9 @@ class ZeroconfThread(threading.Thread):
         return "_centrix_%s._tcp" % t

     def announce(self):
+        """Announce centrix server via Zeroconf/Avahi,
+        for client machines to can find server"""
+
         self.group = dbus.Interface(self.bus.get_object(avahi.DBUS_NAME, self.server.EntryGroupNew()),
                                     avahi.DBUS_INTERFACE_ENTRY_GROUP)
 #         self.group.connect_to_signal('StateChanged', self._entry_group_state_changed)