additional model changes, did away with rel class, fixed rel props

It wasn't returning any matches because when you have `rel_class` set on an association, it changes the cypher query to look for that class. It's a little odd, I noticed it before but never really cared because it worked, but in a setting like this where there's mixed data, it will screw things up.

```
MATCH (movie6589:`Movie`), (person:`Person`), movie6589<-[rel {_classname: "Engagement"}]-(person:`Person`) WHERE ID(movie6589) = 6589 RETURN person, rel
```
That's what the cypher looked like. In this patch, I remove the rel_class entirely. We use the `props` method to get access to the relationship properties but things still aren't working perfectly, I didn't have time to get it all figured out.