Fix babel@6 upgrade regression.

The new module definitions no longer export the default as module.exports unless you use a custom plugin.

.babelrc

@@ -1,3 +1,4 @@
 {
-  "presets": ["es2015", "stage-2"]
+  "presets": ["es2015", "stage-2"],
+  "plugins": ["add-module-exports"]
 }

package.json

@@ -29,6 +29,7 @@
   "devDependencies": {
     "babel-cli": "^6.4.0",
     "babel-core": "^6.4.0",
+    "babel-plugin-add-module-exports": "^0.1.2",
     "babel-preset-es2015": "^6.3.13",
     "babel-preset-stage-2": "^6.3.13",
     "bluebird": "^3.1.1",

test/index.js

@@ -28,6 +28,11 @@ describe('cacheman', function () {
     cache.clear(done);
   });
 
+  it('should return a proper CommonJS module, not an ES6-only one', function() {
+    var mod = require('../node/index');
+    assert.equal(typeof(mod), 'function');
+  });
+
   it('should have main methods', function () {
     assert.ok(cache.set);
     assert.ok(cache.get);