Add language in final extension

TODO: make this an option (with default: deactivated)
Add language in final extension

TODO: make this an option (with default: deactivated)
Merge branch 'feature/language-extension' of https://github.com/souen/ruby-osdb into feature/language-extension
Adding option to add language in the subtitle's file extension
removing trailing tabs
factorizing an affectation
Changing the option -x to -L
Removing a useless .nil? in a condition
Merge pull request #18 from ewandor/feature/language-extension

Option to suffix filename with language code