* Make styled-jsx configurable

* Add styled-jsx-plugin-postcss example

* Add styled-jsx 2.1.0 with plugins support

* Move examples around and add description

* Add link to new example

* Configurable opts for babel-preset-env + babel-plugin-transform-runtime

This adds `preset-env` and `transform-runtime` options to the
`next/babel` Babel preset, which are then passed through to those
presets and transforms. This allows configuration to keep next.js
from the default 'maximum' transform, and instead use built-in
implementations of globals, classes, async, and other commonly-supported
features.

Fixes #2989

* Use spread notation instead of Object.assign

Otherwise, user has to expose it's env variable as development.
Usually, that's unlikely to happen.

Here we don't use the full capabilities of babel-preset-env.
But it's recommended to use it without browser configs as
a substitute for babel-preset-latest.
That's why we did this.

Without this, modules built with Babel or Webpack would have hard-coded absolute paths
all the way back to the root of the filesystem. This prevented compilation and running
on different machines or even from different directories on the same machine.

With this change, paths are hard-coded to the top-most node_madules directory found,
which should make them portable relative to the app.

Fixes #1160

* Remove babell-plugin-transform-react-constant-elements.
With this, our shared-modules example's counter won't work in
production mode. (as this plugin enabled)
So, we could see more issues like this.
That's why we don't need this at this time.

* Update package.json.

* Optimize React

* Remove unused preset

* Remove pure-class-to-function

* Optimize React

* Remove unused preset

* Add babel-preset-2016 support.
This adds the support for Exponentiation operator (**)

* Use babel-preset-latest.

* Remove babel-plugin-transform-async-to-generator in favor of babel-plugin-latest
It has es2017 preset and it comes with the above plugin.

- tackles #997
- add ./idea to gitignore for webstorm users
- update all the examples

* Let webpack2 to handle ES2015 module system
Since Node.js can't do that, we need to transpile
ES2015 module system in the emit-file-loader.

* Use sourceMaps only in dev.

* Introduce a transform option to emit-file-loader
So, we can move our ES2015 transpile code with that option.

* Remove unwanted argument options.

* Update comments.

* Use dev flag instead of NODE_ENV

* Remove default next pages compilation from the main babel-loader.
This will fix the issue when the user ignore node_modules
via our .babelrc option.

* Change babel-loaders 'query' to 'options'.
That's what's supported/recommended in webpack 2

* Create a babel-preset for plugins and presets we use.
Anyone could get it via 'next/babel'

* Remove  'use strict' from the source.

* Add next/router to alias resolver in our babel preset.