use @aws-cdk/cloudformation-diff for diff generation#33

AndrewChubatiuk wants to merge 3 commits intonicka:masternicka/serverless-plugin-diff:masterfrom

AndrewChubatiuk:use-cdk-cfn-diffAndrewChubatiuk/serverless-diff-plugin:use-cdk-cfn-diffCopy head branch name to clipboard