Feature request: Prevent Mac from sleeping while Imagr app is running a workflow

[homebysix]

It would be desirable for Imagr to prevent a Mac from entering sleep while a workflow is running.

For example: Munki uses this module to prevent idle sleep during some operations.

I'd like to contribute a PR, but I'll leave this issue open as a bookmark in case others want to tackle it first.

[homebysix]

Some follow-up: It looks like powermgr is already imported, and all that's necessary is to create a Caffeinator object, like this. I may be able to tackle this after all.