Remove config reload hacks

mixlib-config 2.0 takes care of this without needing to reload config.rb
over and over.
Add a root config_dir config option

Also, refactor path joins in Config to a method that will support
components containing a trailing separator or not.
Fix String element reference for ruby 1.8
Add a directory where trusted certs can be stored
Merge branch 'ssl-cert-dir'