Added Darwin support to the original (8.6+) .tm
Use file join rather than join to create paths
Ensure that our file join will recognize leading /
Ensure Darwin configDirs & dataDirs returns list
Add tests for Darwin
Add brand name and app name for darwin dirs
Use HOME environmental variable not  ~ for Darwin

Also update test_helpers to use /Users instead of /home for Darwin.
Fix bug where XDG::DATA_HOME being used everywhere

This was introduced when changes for Darwin were made.  Fixed and added
tests.
Make Windows *Home directory checks more specific
Change requirements to TclOO instead of Tcl 8.6

This is so that the module can be used with Tcl 8.5.
Add listdirs.tcl to list default & current dirs