Removes `hasOwnProperty` checks to improve overall performance.

Tested using a real application, it can be found [here](https://github.com/stefanpenner/perf-stress).

Fixes #2206.

`normalizeAttributes`

before:
![normalize-attributes-before](https://cloud.githubusercontent.com/assets/1131196/3999543/37a1ce48-2951-11e4-8490-4f696a430637.png)

after:
![normalize-attributes-after](https://cloud.githubusercontent.com/assets/1131196/3999558/5dcdb9a6-2951-11e4-9304-bd4920bf8969.png)

`normalizeRelationships`

before:
![normalize-relationships-before](https://cloud.githubusercontent.com/assets/1131196/3999695/a111ce86-2952-11e4-81da-268aaecc7fb7.png)

after the change, it doesn't get registered.

thanks to @stefanpenner for pointing it out.