[modules/disk] Re-enable disk usage module

Add a module that shows the disk usage for various paths and opens
nautilus on that path whenever it is clicked.

see #23

bumblebee/util.py

@@ -18,6 +18,13 @@ def execute(cmd, wait=True):
         return out.decode("utf-8")
     return None
 
+def bytefmt(num):
+    for unit in [ "", "Ki", "Mi", "Gi" ]:
+        if num < 1024.0:
+            return "{:.2f}{}B".format(num, unit)
+        num /= 1024.0
+    return "{:05.2f%}{}GiB".format(num)
+
 def durationfmt(duration):
     minutes, seconds = divmod(duration, 60)
     hours, minutes = divmod(minutes, 60)