Created by: wangkuiyi

When I tried to follow the "Majel in Paddle" mode described in https://github.com/PaddlePaddle/Paddle/pull/2118#issuecomment-301133925, paddle/CMakeLists.txt didn't add sub-directory majel.

I manually checked and found that the function invocation find_package(boost) must be written as find_package(Boost) as described in https://cmake.org/cmake/help/v3.0/module/FindBoost.html.