doc: clarify module loading behavior

The module loading system will not append node_modules to a path already ending in node_modules. This used to be documented, but it was lost. Fixes: #3873 PR-URL: #3920 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Michaël Zasso <[email protected]>

Author: cjihrig

doc/api/modules.markdown

@@ -339,7 +339,8 @@ example, then `require('./some-library')` would attempt to load:
 If the module identifier passed to `require()` is not a native module,
 and does not begin with `'/'`, `'../'`, or `'./'`, then Node.js starts at the
 parent directory of the current module, and adds `/node_modules`, and
-attempts to load the module from that location.
+attempts to load the module from that location. Node will not append
+`node_modules` to a path already ending in `node_modules`.
 
 If it is not found there, then it moves to the parent directory, and so
 on, until the root of the file system is reached.