README outdated: `setLanguage` is not available anymore

Hi, it looks like this part in the README is not up to date anymore.

```
// setting french as default language...
tmdb.setLanguage('fr');
// and resetting to english.
tmdb.resetLanguage();
```

When I run a file with this I get the following error:

```
tmdb.setLanguage('fr');
     ^
TypeError: tmdb.setLanguage is not a function
```