Got rid of localized movie titles, added ability to customize HTTP fetching

If you try to get a movie info from a country where English is not the main language, IMDB would return localized titles unless you set Accept-Language header to en-US. For example if you search for 'die hard' from a Russian IP address you'd get "Крепкий орешек (1988)" instead of "Die Hard (1988)".
To get rid of it I created a Client class to abstract http fetching, replaced open-uri with net/http and set default language to en-US. 
Now it's easy to replace http retrieval method by implementing Imdb::Client class and passing it to initializers of Search, Movie or other classes. Also you can customize headers by creating an Imdb::Client instance with your headers passed to it's initializer and passing the instance to other Imdb classes.