Check for dependencies while creating a new project

[reznord]

It would be great to have a dependency check so we can avoid running into issues like #165

I would love to add the following code for dependency check.

@rkostrzewski @developit @lukeed any suggestions?

[reznord]

For running the check we have two choices:

• when user installs preact-cli
• when user creates a new project. i.e. while preact create my_app.

In the first case, there might be users who maintain multiple node versions (like me :P) for various projects and that might become a problem

In the second case we can do it as a first step before executing the create command

[lukeed]

You can run the same check at both points.

{
  "postinstall": "node lib/check.js"
}

And

// src/index.js
const check = require('./lib/check');

let isValidNode = check();

if (!isValidNode) {
  return; // already logged
}

installHooks();
// continue...