fix export and import specifier getIds and add support for computed properties to isReferenced

lib/6to5/types/index.js

@@ -128,8 +128,8 @@ t.isDynamic = function (node) {
 };
 
 t.isReferenced = function (node, parent) {
-  // we're a property key so we aren't referenced
-  if (t.isProperty(parent) && parent.key === node) return false;
+  // we're a property key and we aren't computed so we aren't referenced
+  if (t.isProperty(parent) && parent.key === node && !parent.computed) return false;
 
   // we're a variable declarator id so we aren't referenced
   if (t.isVariableDeclarator(parent) && parent.id === node) return false;
@@ -256,8 +256,8 @@ t.getIds = function (node, map, ignoreTypes) {
 
 t.getIds.nodes = {
   AssignmentExpression: "left",
-  ImportSpecifier: "id",
-  ExportSpecifier: "id",
+  ImportSpecifier: "name",
+  ExportSpecifier: "name",
   VariableDeclarator: "id",
   FunctionDeclaration: "id",
   ClassDeclaration: "id",