[modules] Add battery indicator plugin

Add a plugin that displays the remaining battery power in %. This also
introduces the concept of arguments that can be passed to a module
during startup by delimiting the module name with ":", for example:

-m battery:BAT1 to query the BAT1 device.

Note that this works to an arbitray length, i.e. if a module accepts 3
parameters: -m <modulename>:<A>:<B>:<C>

The module gets the arguments as list.

bumblebee/module.py

@@ -1,6 +1,6 @@
 
 class Module(object):
-    def __init__(self, theme):
+    def __init__(self, theme, args):
         self._theme = theme
 
     def theme(self):

bumblebee/modules/battery.py

@@ -0,0 +1,19 @@
+import datetime
+import bumblebee.module
+
+class Module(bumblebee.module.Module):
+    def __init__(self, theme, args):
+        super(Module, self).__init__(theme, args)
+        self._battery = "BAT0" if not args else args[0]
+        self._capacity = 0
+        self._status = "Unknown"
+
+    def data(self):
+        with open("/sys/class/power_supply/%s/capacity" % self._battery) as f:
+            self._capacity = int(f.read())
+        with open("/sys/class/power_supply/%s/status" % self._battery) as f:
+            self._status = f.read().strip()
+
+        return "%02d%%" % self._capacity
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4

bumblebee/modules/time.py

@@ -2,8 +2,8 @@ import datetime
 import bumblebee.module
 
 class Module(bumblebee.module.Module):
-    def __init__(self, theme):
-        super(Module, self).__init__(theme)
+    def __init__(self, theme, args):
+        super(Module, self).__init__(theme, args)
 
     def data(self):
         return datetime.datetime.now().strftime("%x %X")

i3bumblebee

@@ -28,8 +28,10 @@ def main():
     for m in args.modules:
         # TODO: how to cleanly handle errors here?
         # (useful error messages)
-        module = importlib.import_module("bumblebee.modules.%s" % m)
-        modules.append(getattr(module, "Module")(theme))
+        module_name = m if not ":" in m else m.split(":")[0]
+        module_args = None if not ":" in m else m.split(":")[1:]
+        module = importlib.import_module("bumblebee.modules.%s" % module_name)
+        modules.append(getattr(module, "Module")(theme, module_args))
 
     output = bumblebee.outputs.i3.i3bar()