If you set up your package using rstan_package_skeleton() before
version 1.2.1 of rstantools it may be necessary for you to call
this function yourself in order to pass R CMD check in R
>= 3.4. If you used rstan_package_skeleton() in rstantools version
1.2.1 or later then this has already been done automatically.
init_cpp(name, path)This function is only called for its side effect of writing the
necessary init.cpp file to the package's src/ directory.
The name of your package as a string.
The path to the root directory for your package as a string. If not specified it is assumed that this is already the current working directory.