[modules] Add support for disk utilization

Add a new module "disk" that takes an optional parameter (the path) and
displays free & total disk space, along with the usage percentage.

Also, added Tunnel/VPN support to the themeing of the "net" module.

bumblebee/modules/disk.py

@@ -0,0 +1,25 @@
+import os
+import bumblebee.util
+import bumblebee.module
+
+class Module(bumblebee.module.Module):
+    def __init__(self, args):
+        super(Module, self).__init__(args)
+        self._path = args[0] if args else "/"
+
+    def data(self):
+        st = os.statvfs(self._path)
+
+        self._size = st.f_frsize*st.f_blocks
+        self._free = st.f_frsize*st.f_bavail
+        self._perc = 100.0*self._free/self._size
+
+        return "{} {}/{} ({:05.02f}%)".format(self._path, bumblebee.util.bytefmt(self._free), bumblebee.util.bytefmt(self._size), self._perc)
+
+    def warning(self):
+        return self._perc < 20
+
+    def critical(self):
+        return self._perc < 10
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4