Update aws-sdk dependency to match gulp-awspublish
Update aws-sdk dependency to match gulp-awspublish

The current `aws-sdk` dependency version is not exactly the same as the `aws-sdk` used for `aws-publish`. This means that when installing `gulp-cloudfront-invalidate-aws-publish` and `gulp-awspublish` there are two different versions of the `aws-sdk` in the node_modules folder.

Making the dependency specifications the same reduces the size of `node_modules` by at least 5 MB.

lpender/gulp-cloudfront-invalidate-aws-publish