(maint) Update debian packaging to reverence new rack support location

As updated in commit 4c9b63f, the sample files for rack passenger deployment
have been moved up a directory. The puppetmaster-passenger package for debian
uses those files, so this commit updates the debian/rules file with their new
location. It also updates the README_DEVELOPER.md, which references the same
files.
Merge pull request #1 from haus/stale_rack_files

(maint) Update debian packaging to reverence new rack support location