Improve documentation to help ease the transition from 0.6 to 1.0?

[richardwestenra]

I've spent many hours trying to work out why my grunt-modernizr build no longer worked after setting up an old project on a new laptop. I get that breaking changes are sometimes inevitable, but I can't be the only one in this situation. I needed to make a bunch of config changes in order to get things working again, and the fixes were not always obvious.

Would you welcome a PR to add documentation on the upgrade process, and how to reconfigure your grunt-modernizr settings to restore the old functionality? I was thinking of adding a separate updatedocs.md file in the root, and linking to it from the main readme. I might need some guidance/feedback on the wording because I haven't been closely involved with the Modernizr project, but I'm happy to get it started.

[patrickkettner]

PRs are always welcomed