[modules] Add layout-xkb using xkbgroup to display current layout

Package xkbgroup as "thirdparty", because it was slightly patched
for python2.x compatibility.

see #177

bumblebee/modules/layout-xkb.py

@@ -0,0 +1,36 @@
+# pylint: disable=C0111,R0903
+
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
+
+from thirdparty.xkbgroup import *
+
+import logging
+log = logging.getLogger(__name__)
+
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.current_layout)
+        )
+        engine.input.register_callback(self, button=bumblebee.input.LEFT_MOUSE,
+            cmd=self._next_keymap)
+        engine.input.register_callback(self, button=bumblebee.input.RIGHT_MOUSE,
+            cmd=self._prev_keymap)
+
+    def _next_keymap(self, event):
+        self._set_keymap(1)
+
+    def _prev_keymap(self, event):
+        self._set_keymap(-1)
+
+    def _set_keymap(self, rotation):
+        pass
+
+    def current_layout(self, widget):
+        xkb = XKeyboard()
+        log.debug("group num: {}".format(xkb.group_num))
+        return "{} ({})".format(xkb.group_symbol, xkb.group_variant) if xkb.group_variant else xkb.group_symbol
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4