add babel-preset-es2015

[gimdongwoo]

#2

src/controllers/index.js

const a = 'test';

var doClick = (e) => {
  alert($.label.text + a);
}

$.index.open();

This is transcoded result.

app/controllers/index.js

'use strict';

var a = 'test';

var doClick = function doClick(e) {
  alert($.label.text + a);
};

$.index.open();

I think ES2015 (ex: arrow functions, const, let) are already used as standard, so we need es2015 preset.

Thank you.

[vladm3]

@gimdongwoo Please see my comment under the issue #2