Take special care of movie rating values when they're not set.

"N/A" values or others that are parsed as NaN are saved as -1 in the store.
jshint enforces the use of brackets in if statements

If you run `ember build` in the shell, you'll see this error message

```
controllers/movie.js: line 7, col 7, Expected '{' and instead saw 'return'.
controllers/movie.js: line 9, col 7, Expected '{' and instead saw 'return'.
controllers/movie.js: line 15, col 7, Expected '{' and instead saw 'return'.
controllers/movie.js: line 17, col 7, Expected '{' and instead saw 'return'.

4 errors
```