Add a new test which fails.
Fix building of the search path when searching for relative includes.
 - Use some simple inline logic instead of the more complex (and buggy) getRelative in file-utils
 - Add tests to cover my changes
 - We now properly search the path of the file being read *first*, and then consult ConfigPath, to retain compatibility with Config::General from Perl
 - Strip trailing slashes from directory names before appending '/' + file name