Fix stock market example [Good for first time contributors]

[tomastrajan]

The stock market example was getting data from google finance API which seems to be discontinued. We have to find another free source of simple stock prices to consume and use it in stock-market.service.ts.

Based on the shape of retrieved data (JSON), additional adjustments to map functions might be needed.

Original Google finance API url: https://finance.google.com/finance?output=json&q=NYSE:

Tips for first time contributors:

1. Create fork of the repository
2. Create fix commit in format fix(examples): fix stock market API source or something similar
3. Create pull request (Github) should offer that option automatically once the fix branch was pushed

[tomastrajan]

Was fixed by #162 by @shootermv, thanks again!