18: added c++ library

Closes #18

cpp/CMakeLists.txt

+cmake_minimum_required(VERSION 3.10)
+project(demo)
+
+set(CMAKE_CXX_STANDARD 14)
+
+add_executable(demo demo.cpp)
+
+find_package(OpenSSL REQUIRED)
+find_package(CURL REQUIRED)
+
+include_directories(${CURL_INCLUDE_DIR} ${OPENSSL_INCLUDE_DIR})
+target_link_libraries(demo ${CURL_LIBRARIES} ${OPENSSL_LIBRARIES})