(maint) Render modules lists as pson in acceptance tests

The module_utils lib assists the acceptance tests in setting up, tearing
down and verifying module state.  The get_installed_modules_for_host
method used to list modules with the 's' (to_s) renderer, which produces
different output for different major ruby versions due to changes in
to_s.  In Ruby 2.0 the output no longer matches our search pattern.

This patch switches to pson rendering which produces the same output
for all versions, ensuring that we can find module paths with a single
sane regex.
(maint) Fix acceptance test_against_preserved_hosts task

An option to set the CONFIG_NUMBER to test against previous runs earlier
than the most recent was not working because I failed to convert the
parameter to an int.  This changes that.
(docs) Document additional parameters needed to curl with ssl

Some additional notes documenting how to curl the puppet master using
all the necessary ssl parameters for authentication.