Speedup compilation (#370)

Adding --parallel option to cmake to compile faster

Signed-off-by: Jakub T. Jankiewicz <jcubic@onet.pl>

Author: jcubic

README.md

@@ -28,7 +28,7 @@ Project is defined using [CMake](https://cmake.org/).
 mkdir build
 cd build
 cmake .. -D CMAKE_BUILD_TYPE=Release
-cmake --build . --target package
+cmake --build . --target package --parallel $(nproc)
 cmake --build . --target install
 ```