path: use '===' instead of '==' for comparison

Per: nodejs/node-v0.x-archive#7554

Originally submitted by @stites

PR-URL: #2388
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>

Author: Sam Stites

lib/path.js

@@ -277,7 +277,7 @@ win32.relative = function(from, to) {
     }
   }
 
-  if (samePartsLength == 0) {
+  if (samePartsLength === 0) {
     return to;
   }