Use the same CXX for matcaffe as for the rest of the build
Merge pull request #766 from rbgirshick/matcaffe-cxx

Use the same CXX for matcaffe as for the rest of the build
numerical stability improvement
Merge pull request #773 from qipeng/lrelu

Leaky ReLU numerical stability improvement
Solver switching support & implementation of Nesterov's accelerated gradient and AdaGrad
restored vituals in solver.hpp
converted pointers to shared_ptr
fixed solver constructor in train_net.cpp
improved numerical stability for AdaGrad
bugfixes for AdaGrad