Use this module to prevent your Mac OS X system from sleeping while executing
a long-running python script.

Quick Start
-----------

Just `import caffeine`.  That's it!  You Mac OS X system will not sleep as 
long as the interpreter remains alive.  No need to run any other commands.
But if you want slightly finer controls, a few functions are available.

`caffeine.on(display=False)`

Use the `on` function to create a power assertion.  Set display=True to also
keep your display from sleeping. The default of display=False will allow
your display to sleep but will keep your system awake so processing can
continue.  If a power assertion is active, calling `on()` with display set
to the other value will change the assertion.  Calling `on()` with the same 
value is a harmless no-op.

`caffeine.off()`

Use the `off` function to release any power assertion before your interpreter
exits.

`caffeine.verify()`

Calls `pmset -g assertions` to verify what power assertions are active.