Add instructions on Heroku and Lambda deployment

[Glogo]

Add instructions to README documenting deployment to Heroku and Lambda

Notes:

Heroku

• add script "npm start" to package.json
• create heroku account, install toolbelt, login
• heroku create [app-name]
• copy server url to amazon developer portal
• emphasize that heroku requires process.env.PORT env variable to be used as server port (it is used by default)

AWS Lambda

• create lambda function with handler f.e. index.handler and with Alexa Skills Kit trigger
• copy lamba function arn into amazon developer portal
• zip and upload src with bundled node_modules
• (optional) consider creating "zip script" to automate this (upload needs to be manual though)
• add to index.js:

/* Create or require app here ... */

exports.handler = (event, context, callback) => {
    app.handle(event, data => {
        callback(null, data);
    });
};

[chrischang]

How detailed instructions do you want for Heroku? I have just built an app with Alexia and have deployed it to Heroku successfully, so I am wondering maybe if I could help with this task.

[Glogo]

Just some basic steps required for the deployment (mentioned in the lists in issue description). I already started writing something for both Heroku and Lambda.

I will create pull request in a minute so you can take a look at it and update it if necessary