Resolving the error "TypeError: Object #<Query> has no method 'run'"

On call model.submodel.populate() throws this error. It seems that the method `run` was deplicated.

```TypeError: Object #<Query> has no method 'run'
    at Array.MongooseArray.populate (/home/user/dev/nodejs/marqet-express/node_modules/mongo-relation/lib/relationships.js:320:6)```
Merge pull request #3 from Tolsi/master

Resolving the error "TypeError: Object #<Query> has no method 'run'"