support import() as contextual import in system module format

packages/babel-plugin-transform-es2015-modules-systemjs/test/fixtures/systemjs/dynamic-import/actual.js

@@ -0,0 +1,6 @@
+export function lazyLoadOperation () {
+  return import('./x')
+  .then(function (x) {
+    x.y();
+  });
+}

packages/babel-plugin-transform-es2015-modules-systemjs/test/fixtures/systemjs/dynamic-import/expected.js

@@ -0,0 +1,16 @@
+System.register([], function (_export, _context) {
+  "use strict";
+
+  function lazyLoadOperation() {
+    return _context.import('./x').then(function (x) {
+      x.y();
+    });
+  }
+
+  _export('lazyLoadOperation', lazyLoadOperation);
+
+  return {
+    setters: [],
+    execute: function () {}
+  };
+});