How to use cpp11armadillo?

1. Open `./dev/01_load_or_install.R` and run it.
2. Open `./src/01_ols.cpp`, inspect the OLS functions.
3. Create your own functions in `./02_your_functions.cpp`. Feel free to rename
   the file and delete the OLS example.
4. Run `devtools::load_all()` in `./dev/01_load_or_install.R` to test your
   functions.
5. Run `./dev/03_readme_and_license.R` to add a README and license.
6. Run `devtools::install()` in `./dev/01_load_or_install.R` to install the
   package locally when you are ready.
7. The package template includes a configuration script that sets up the package
   to use 50% of the available cores. You can change this value directly in
   `./src/Makevars` or adapting `./configure`.
