Displays Incorrect Number of Stars

## I'm submitting a...

[x] Bug report  

[ ] Feature request

## Current behavior

Setting numOfStars greater than 5 and setting to rating to greater than 5 never displays more than 5 stars

## Expected behavior

Display correct number of stars according to rating value

## Minimal reproduction of the problem with instructions

https://stackblitz.com/edit/angular-star-rating-demo-rtdndy?file=app%2Fapp.component.html

## Environment

Library version: 4.0.0

Angular version: 6.Y.Z


Browser:

- [ ] Chrome (desktop) version XX