style(rxApp): Change colors for pre-prod menu

Closes #538 

When a product is in the `preprod` environment (i.e. `https://preprod.encore.rackspace.com`), put a warning banner on the top of the screen and change the nav menu colours.

This PR also adds the `preprod` environment. Before, we had `unified-preprod`, which means "anything that's not `production`". We still have that, but `preprod` is now its own identifiable environment.

![screen shot 2014-09-24 at 2 57 27 pm](https://cloud.githubusercontent.com/assets/9376/4394050/9e97b748-441d-11e4-9858-b530f16e3e8c.png)
Does this need to be a function (see alternative below)? In theory, we should only have to check for this on page load. We won't be changing environments without reloading the entire page, so evaluating it on the fly shouldn't be needed. 

```
scope.isPreProd = Environment.get().name === 'preprod';
```