Download link in README.md is wrong

[rjk]

The Step 2 download link in README.md is to https://github.com/training4developers/ng2-widgets-app instead of ..../mastering-angular-starter. Using that link leads to much confusion since the project doesn't build for the same reason as the most recent fixed issue in this repo :)

[ericwgreene]

Thank you for catching that! I have fixed it. Please verify. Thanks!