Fixed minor typo in docs
Fixed minor typo in docs

opip > pip
Stranger6667/django-hstore,Stranger6667/django-hstore,Stranger6667/django-hstore,pombredanne/django-hstore,djangonauts/django-hstore,pombredanne/django-hstore,djangonauts/django-hstore,djangonauts/django-hstore,pombredanne/django-hstore,Stranger6667/django-hstore,pombredanne/django-hstore,djangonauts/django-hstore