Insufficient info for installing the package

The info in the ReadMe is not enough for installing the package, especially if the person willing to do that is a monkey-tester. :)

First, the sd branch of airGR does not exist anymore. Please replace with the dev branch, which is I think the branch that contains the SD model.

Second, the instruction run roxygen for generating NAMESPACE file and documentation does not mean much for newbies. Could you be more specific with this instruction?