add some new s3-related context variables when publishing site
add some new s3-related context variables when publishing site

NUKnightLab/tarbell,eyeseast/tarbell,tarbell-project/tarbell,eyeseast/tarbell,NUKnightLab/tarbell,NUKnightLab/tarbell,eads/tarbell,tarbell-project/tarbell,eads/tarbell