Make callback parameters optional
Make callback parameters optional

chrisradek/aws-sdk-js,aws/aws-sdk-js,chrisradek/aws-sdk-js,chrisradek/aws-sdk-js,aws/aws-sdk-js,GlideMe/aws-sdk-js,GlideMe/aws-sdk-js,aws/aws-sdk-js,GlideMe/aws-sdk-js,aws/aws-sdk-js,chrisradek/aws-sdk-js,GlideMe/aws-sdk-js