[modules] Add module for measuring CPU utilization

Add module "cpu", which uses psutil to measure CPU utilization between
two consecutive calls.

bumblebee/modules/cpu.py

@@ -0,0 +1,20 @@
+import bumblebee.module
+import psutil
+
+class Module(bumblebee.module.Module):
+    def __init__(self, args):
+        super(Module, self).__init__(args)
+        self._perc = psutil.cpu_percent(percpu=False)
+
+    def data(self):
+        self._perc = psutil.cpu_percent(percpu=False)
+
+        return "{:05.02f}%".format(self._perc)
+
+    def warning(self):
+        return self._perc > 70
+
+    def critical(self):
+        return self._perc > 80
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4