Support directory traversal to find package root when loading and unloading
Update NEWS.md to reflect support for directory traversal to find package root
check that path is character in package_root
Use is_root helper per @hadley
Test package loading
Use is_root helper in recursive traversal as well
Incorporate small changes per @hadley
Merge pull request #616 from robertzk/load_from_anywhere

Support directory traversal to find package root