custom data property tests
custom data property tests

assert that:

* reserved properties are removed
* other custom properties are retained
stormpath/stormpath-sdk-node,wakashige/stormpath-sdk-node,ck-lee/stormpath-sdk-node,peebles/stormpath-sdk-node,peebles/stormpath-sdk-node,stormpath/stormpath-sdk-node