Use -p flag in webpack for minification and exclude externals react a…

[doque]

Fixes #144 .

Changes proposed:

• Use webpack -p for minification instead of UglifyJS Plugin
• Designate react and react-dom as externals in webpack config to exclude them from build

Reduces minified build size to 14.4kB.

[diasbruno]

This seems really nice. I'll test it.

[diasbruno]

We already know the numbers, but just to validate.

With build script and browserify:

react-modal.js     53K
react-modal.min.js 22K

With webpack:

• reactjs/development-improvements:

             Asset    Size  Chunks             Chunk Names
    react-modal.js  719 kB    0, 1  [emitted]  react-modal
react-modal.min.js  190 kB    1, 0  [emitted]  react-modal.min

• doque/development-improvements:

             Asset     Size  Chunks             Chunk Names
    react-modal.js    57 kB    0, 1  [emitted]  react-modal
react-modal.min.js  14.4 kB    1, 0  [emitted]  react-modal.min

This is awesome, @doque.

[diasbruno]

@doque It seems that without -p has the same effect as using webpack.optimize.UglifyJsPlugin, the file size i got are the same.