Use https for staging as well

Shouldn't staging use https as well or am I missing something?

I can't view the integrations in staging because it requests http when I'm actually on ssl. (Firefox blocks them).

```
23:07:25.187 Blocked loading mixed active content "http://staging.hub.spreecommerce.com/api/stores/52e271e6755b1c382100000e/preprocessors"[Learn More] 
```

My guess is that the environment was created with the url holding the http protocol. 

```
23:08:32.771 Augury.SignUp.urls['staging']
23:08:32.773 "http://staging.hub.spreecommerce.com"
```

Is that right? // @phstc @brian @LBRapid