Rename and update ru pymorphy2 lookup lemmatize
Rename and update ru pymorphy2 lookup lemmatize

* To allow default lookup lemmatization with a blank Russian model,
rename pymorphy2 lookup mode to `pymorphy2_lookup`

* Bug fix: update pymorphy2 lookup lemmatize to return list rather than
string

honnibal/spaCy,honnibal/spaCy,explosion/spaCy,explosion/spaCy,honnibal/spaCy,explosion/spaCy,explosion/spaCy,explosion/spaCy,explosion/spaCy,honnibal/spaCy