Support for OOTB isomorphic rendering

[robframpton]

It's currently possible to achieve server side rendering of Metal.js components, but it requires libraries such as https://www.npmjs.com/package/jsdom to accomplish.

// Node.js 
const JSDOM = require('jsdom').JSDOM;

const { document } = (new JSDOM()).window;

global.document = document;
global.window = document;

const Component = require('metal-component').Component;

const MyComponent = require('./MyComponent').MyComponent;

const htmlString = Component.renderToString(MyComponent);

However, it would be nice to have out of the box isomorphic rendering.

// Node.js 
const Component = require('metal-component').Component;

const MyComponent = require('./MyComponent').MyComponent;

const htmlString = Component.renderToString(MyComponent);

I have sent the following three pull requests relating to server side rendering of components.

#264 (metal-dom)
#265 (metal-soy)
#266 (metal-incremental-dom)

With these changes the second code snippet above should work correctly in a Node.js environment. Once/if these branches are merged, I would like to create a server side integration test separate from the current testing environment we have set up for this repo to test this functionality.

Update: I've sent another PR that adds a simple test for server side rendering.

#269

[brunobasto]

Awesome, Rob!

[jbalsas]

Nice!!

@Robert-Frampton, following the example of the WebComponents story, could we prepare a guide on top of https://github.com/Robert-Frampton/metaljs.com/commits/tutorials?

[robframpton]

Hey @jbalsas

I sent a separate PR bryceosterhaus/metaljs.com#70.

[jbalsas]

All pieces have been merged into develop!