Add favicon to the generated app

[gaearon]

Seems like a nice thing to do + we need to figure out how to do it with webpack 😄

[keyz]

I think html-webpack-plugin supports that. Do we want to put it under template/src?

[keyz]

#70

[gaearon]

#70 (comment)

[modernserf]

The app doesn't build if favicon.ico is missing:

> react-scripts start
Starting the development server...
Failed to compile.

Error in   Error: HtmlWebpackPlugin: could not load file /Users/modernserf/work/src/github.com/modernserf/c  ritter/favicon.ico

  - index.js:303
    [critter]/[react-scripts]/[html-webpack-plugin]/index.js:303:27

[gaearon]

@modernserf Good point. Let’s discuss in #96.