test(pageObjects): Added rxEnvironment Page Object

Added a page object for rxEnvironment. getEnv returns the current environment.
Any chance I could convince you to make this an IIFE?

```js
current: (function () {
    var environments = [
        'localhost',
        'staging',
        'preprod'
    ];

    return _.find(environments, function findEnvironment (env) {
        if (_.contains(browser.baseUrl, env)) {
            return env;
        }
    }) || 'production';
})(),
```