update install script to include knitr
update install script to include knitr

LanceFiondella/srt.core,LanceFiondella/srt.core,arhik/srt.core,LanceFiondella/srt.core,arhik/srt.core,LanceFiondella/srt.core,LanceFiondella/srt.core,arhik/srt.core,arhik/srt.core,LanceFiondella/srt.core