Merge pull request #2903 from ronghanghu/multi_gpu

Multi-GPU Data Parallelism

diff --cc include/caffe/solver.hpp
Simple merge

diff --cc src/caffe/net.cpp
Simple merge

diff --cc src/caffe/proto/caffe.proto
Simple merge

diff --cc src/caffe/solver.cpp
Simple merge

diff --cc src/caffe/test/test_gradient_based_solver.cpp
Simple merge