refactor: use the system loaders for caching environment require.
refactor: use the system loaders for caching environment require.

* lib/specl/runner.lua (initenv): Don't do a manual walk over the
package.path, use the provided `package.loaders`.

Signed-off-by: Gary V. Vaughan <f9023000f29773649f3850298becb9544b5fd6a9@gnu.org>

gvvaughan/specl