Update README.md - Using Resources

Promises aren't unwrapped automatically anymore.
It's deprecated since angular.js 1.2.0-rc.3 - see: https://github.com/angular/angular.js/commit/fa6e411da26824a5bae55f37ce7dbb859653276d
Merge pull request #132 from schmijos/patch-1

Update README.md - Using Resources