[travis] Build Ceres, SuiteSparse, Boost and Eigen externally in travis cache (poparteu/openMVG#159)
[travis] Build Ceres, SuiteSparse, Boost and Eigen externally in travis cache (poparteu/openMVG#159)

poparteu/openMVG#51

poparteu/openMVG,poparteu/openMVG,poparteu/openMVG,poparteu/openMVG