Dev 1.0

For the method "checkIfHighScore:", I think it's better to have 2 separate methods for checking of high score, and setting for the new high score po :bow: 
* -(BOOL) isHighScore (method to return a boolean value):
       - will just compare the current high score and new score
* -(void) updateHighScore (method to set the new score)

Then instead of 
```[self checkIfHighScore:score];```
Use:
```
if (isHighScore:score) {
   [self updateHighScore:score]; 
}
```