Added some more documentation to the get_regex_results function.
Remove the abstractproperty attribute from the languages_in_use so we won't need to verride it in every provider.
Finished the implementation of the versions extracting method.
Fixed type in opensubtitles's provider.
Fixed the documentation of the get_title_by_query method.
Modified the implementation of Opensubtitle's get_title_versions into a shorter and easier to read one (moved most of the code to two helper methods).