Option to force running on all files

[chrisirhc]

I was wondering if there was anyone else who would value adding perhaps a --skip-newer or --newer-all-files option where you can skip the checking for newer files and just run on all files in the source files.

This way, users of this task can use newer: on most of their tasks and if they need to, they can run on all files whenever they need.

The specific case I encountered is where I have a task and an option that sets a configuration on that task, that task doesn't re-run when the option is given. For example, if I want to add source maps via an option, I need to re-run that minification task on all files even if they haven't changed.

I'm happy to submit a PR for this if anyone else finds it useful.