zepto-webpack

Since webpack ProvicePlugin can only be used when $ is directly derived from a module,

current modules can't be used conviently in webpack since their exports.$ is what we got.
Current version of Zepto: ``1.2.0``
Version of this repo: ``1.2.0``
Official releases: github.com/madrobby/zepto/releases``npm install zepto-webpack``

plugins: [
    new webpack.ProvidePlugin({
        $: 'zepto-webpack'
    })
]

at line 887 I add:

module.exports = window.Zepto;

solve ajax issue in issue921