Update documentation with additional prerequisites
Update documentation with additional prerequisites

Pillow 3+ requires libjpeg and zlib.

Also note that npm 4.x should be installed on RHEL.

data-exp-lab/girder,essamjoubori/girder,Xarthisius/girder,adsorensen/girder,manthey/girder,RafaelPalomar/girder,salamb/girder,essamjoubori/girder,adsorensen/girder,Xarthisius/girder,data-exp-lab/girder,adsorensen/girder,kotfic/girder,girder/girder,jbeezley/girder,salamb/girder,adsorensen/girder,manthey/girder,kotfic/girder,sutartmelson/girder,Kitware/girder,Xarthisius/girder,sutartmelson/girder,Xarthisius/girder,Xarthisius/girder,RafaelPalomar/girder,salamb/girder,RafaelPalomar/girder,data-exp-lab/girder,essamjoubori/girder,Kitware/girder,kotfic/girder,RafaelPalomar/girder,girder/girder,salamb/girder,adsorensen/girder,girder/girder,kotfic/girder,jbeezley/girder,manthey/girder,sutartmelson/girder,salamb/girder,sutartmelson/girder,Kitware/girder,sutartmelson/girder,essamjoubori/girder,jbeezley/girder,manthey/girder,girder/girder,data-exp-lab/girder,Kitware/girder,data-exp-lab/girder,RafaelPalomar/girder,essamjoubori/girder,kotfic/girder,jbeezley/girder