add comments to display what module syntax each part handles

lib/6to5/transformers/modules.js

@@ -8,7 +8,7 @@ exports.ImportDeclaration = function (node) {
 
   if (node.specifiers.length) {
     _.each(node.specifiers, function (specifier) {
-      var variableName = specifier.name || specifier.id;
+      var variableName = getSpecifierName(specifier.name);
       var key          = specifier.id.name;
 
       // import foo from "foo";
@@ -28,6 +28,7 @@ exports.ImportDeclaration = function (node) {
       }));
     });
   } else {
+    // import "foo";
     nodes.push(util.template("require", {
       MODULE_NAME: node.source.raw
     }, true));
@@ -38,14 +39,16 @@ exports.ImportDeclaration = function (node) {
 
 var pushExportSpecifiers = function (node, nodes) {
   _.each(node.specifiers, function (specifier) {
-    var variableName = specifier.name || specifier.id;
+    var variableName = getSpecifierName(specifier);
 
     if (node.source) {
       if (specifier.type === "ExportBatchSpecifier") {
+        // export * from "foo";
         nodes.push(util.template("exports-wildcard", {
           MODULE_NAME: node.source.raw
         }, true));
       } else {
+        // export { foo } from "test";
         nodes.push(util.template("exports-require-assign-key", {
           VARIABLE_NAME: variableName.name,
           MODULE_NAME:   node.source.raw,
@@ -53,6 +56,7 @@ var pushExportSpecifiers = function (node, nodes) {
         }, true));
       }
     } else {
+      // export { foo };
       nodes.push(util.template("exports-assign", {
         VALUE: specifier.id,
         KEY:   variableName
@@ -61,6 +65,10 @@ var pushExportSpecifiers = function (node, nodes) {
   });
 };
 
+var getSpecifierName = function (specifier) {
+  return specifier.name || specifier.id;
+};
+
 var pushExportDeclaration = function (node, parent, nodes) {
   var declar = node.declaration;