Add log option

[schoenwaldnils]

I added an option to see when a file is updated/generated.
Sadly the v for verbose is already used for version, so I used lfor log

[watilde]

LGTM

[RyanZim]

@schoenwaldnils @watilde Shouldn't this be rebased into one commit?

[watilde]

@RyanZim yeah it would be nicer, or I will cherry-pick it like the last release #19

[RyanZim]

@watilde You could also squash-merge it: https://github.com/blog/2141-squash-your-commits.

[moll]

I'd like to see this merged in, too, as it's very unclear when PostCSS has finished processing when watching. However, I'd say go with --verbose and possibly -V if nothing else to be consistent with every other thing. ;-)

[watilde]

This PR is shipped as 90ad9df. Thanks for making improvements in the new feature!