Omit name from shrinkwrap when not needed

Now that we load the name when creating Node objects in loadVirtual,
there's no need to include it in the shrinkwrap metadata entry.

PR-URL: #74
Credit: @isaacs
Close: #74
Reviewed-by: @ruyadorno

lib/shrinkwrap.js

@@ -86,7 +86,7 @@ const maybeStatFile = file => {
 }
 
 const pkgMetaKeys = [
-  'name',
+  // note: name is included if necessary, for alias packages
   'version',
   'dependencies',
   'peerDependencies',
@@ -172,6 +172,10 @@ class Shrinkwrap {
       if (val)
         meta[key.replace(/^_/, '')] = val
     })
+    // we only include name if different from the node path name
+    const pname = node.package.name
+    if (pname && pname !== node.name)
+      meta.name = pname
 
     if (node.isTop && node.package.devDependencies)
       meta.devDependencies = node.package.devDependencies