Incorrect progress counting

[bocharsky-bw]

It's a bit tricky, but I think it could be considered as incorrect progress counting, let me show an example:

Suppose, I have 3 different translation keys in total: foo, hello, and world.
And I have 2 languages, but each one has only 2 different of them:

# messages.en.yml
foo: bar
hello: Hello

# messages.ru.yml
hello: Привет
world: Мир

i.e. if 2 of them are translated into English and another 2 of them are translated into Russian - I have for both:

Total progress for this language: 100%

But I expected to see 66% for both

[Nyholm]

Fixed by #172