This R package relies on Cargo, the Rust package manager. Cargo can be provided
in a number of ways. Either of the following methods should work (although the
first method will guarantee that the most recent version is installed):

1. Install from https://rustup.rs, an official Rust website, e.g.:

   Linux / MacOS:
   * Run: curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- --no-modify-path -y

   Windows:
   * Download rustup-init.exe from https://rustup.rs
   * Open the terminal in the directory in which rustup-init.exe was downloaded
   * Run: .\rustup-init.exe --no-modify-path -y --default-host x86_64-pc-windows-gnu

   If you do not mind having the script modify your PATH environment variable, remove the
   "--no-modify-path" argument. Having Cargo's bin directory in your PATH environment variable is
   *not* necessarily, however, as the R package will still be able to find the 'cargo' executable
   in the $HOME/.cargo/bin directory.

OR

2. Install from a package manager and let 'cargo' by found using the $PATH
   environment variable, e.g.:

   Debian:  sudo apt install cargo
   Ubuntu:  sudo apt install cargo
   Fedora:  sudo dnf install cargo
   macOS:   brew install rust