Added language parameter to APIManager

• #391: You can set the language locale when initializing the APIManager enabling it return a localized verison of the patch notes. It defaults to nil which is the same as passing in en_us. More information can be found here: https://developer.apple.com/library/archive/documentation/AudioVideo/Conceptual/iTuneSearchAPI/Searching.html#//apple_ref/doc/uid/TP40017632-CH5-SW1

Thanks to @kientux for this change.