The imports argument to make_packages() can be a list, with one
value for each package.
The packages are installed using the --no-test-load argument now.
The reason for this, is that install.packages runs in a new R session,
with potentially different library directories, and some required
might not be available when the load test is performed.
make_packages() now has a quiet argument, set to FALSE
to see the installation of disposable packages. This is mainly
useful for debugging.R CMD check warnings and notes.First version on CRAN.