Update PyMongo requirement to v2.8
Update PyMongo requirement to v2.8

Version 2.8 of PyMongo is necessary for full support of MongoDB 3.0.

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