Update franc to 0.2.0
Update language detection in API

Previous versions of retext-language detected languages on
paragraphs and documents by calculating the average of their
children (sentences, paragraphs). This wasn't working for
multi-language parents. For example, when a paragraph included
two sentences, one in English and one in French, their parent
would get their average, something like Catalan.

Now, the API only looks at the primary language for a sentence,
which in my tests results in better results. The paragraph's
primary language is either French or English, and it's languages
are both French and English.
Update spec for a9e7794
Update changelog for 0.2.0
0.2.0