feat(task): acknowledge the user what urls have been changed

When using this task, I would like to see exactly what urls have been changed just like other grunt tasks. Especially work with grunt-usemin, the blocks are replaced so the scripts are not cdnified and this might confuse users. google-cdn needs to be modifed so also submitted a PR there https://github.com/passy/google-cdn/pull/22
I think that output would look a bit confusing. Perhaps drop the `<script src=` part?