message: Updated README.md to explain how installation of json_fwd.hpp can be achieved as part of install step.
diff: @@ -65,7 +65,7 @@ using json = nlohmann::json;
  to the files you want to use JSON objects. That's it. Do not forget to set the necessary switches to enable C++11 (e.g., `-std=c++11` for GCC and Clang).
  -You can further use file [`develop/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/develop/json_fwd.hpp) for forward-declarations.
  +You can further use file [`develop/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/develop/json_fwd.hpp) for forward-declarations. The installation of json_fwd.hpp (as part of cmake's install step), can be achieved by setting `-DJSON_MultipleHeaders=ON`:
  ### Package Managers
  