fix(controller): add timezone back to API

#2183 standardized datetime fields in the API with the rest of the platform. However, this format is missing the timezone, which was important for determining when the model was created.

Current output of `deis releases` without this change (PST compared to UTC):

```
><> deis releases
=== go Releases
v2      -6 hours -57 minutes ago test deployed deis/example-go:latest
v1      -6 hours -56 minutes ago test created initial release
```

With this change:

```
><> deis releases
=== go Releases
v2      48 minutes ago           test deployed deis/example-go:latest
v1      48 minutes ago           test created initial release
```