test(babel-plugin-espower): do not use preset since it makes too much assumption

Author: twada

package.json

@@ -19,7 +19,6 @@
   },
   "devDependencies": {
     "babel-core": "^6.0.10",
-    "babel-preset-es2015": "^6.0.0",
     "mocha": "^2.2.4"
   },
   "directories": {

test/test.js

@@ -10,7 +10,6 @@ function testTransform (fixtureName, extraOptions) {
         var fixtureFilepath = path.resolve(__dirname, 'fixtures', fixtureName, 'fixture.js');
         var expectedFilepath = path.resolve(__dirname, 'fixtures', fixtureName, 'expected.js');
         var result = babel.transformFileSync(fixtureFilepath, extend({
-            presets: ['es2015'],
             plugins: ['../index']
         }, extraOptions));
         var actual = result.code;