added download button for lda topics
added download button for lda topics

XSEDEScienceGateways/textgateway,wrathematics/TAG,XSEDEScienceGateways/TAG,XSEDEScienceGateways/TAG,wrathematics/TAG,wrathematics/TAG,XSEDEScienceGateways/textgateway,XSEDEScienceGateways/textgateway,XSEDEScienceGateways/TAG