TopBarLayout with fixed top bar

I've talked with @gabrielpoca about this and I think I agree with him in this matter:
When we want to reuse a variable inside a component, there might be a few solutions for that, but none should force you to nest the component's descendants in order to reuse it.
So for this particular case you could do something like namespacing the variable even though we're exposing it to the whole stylesheet:
```
$top-bar-layout-height: 62px

.TopBarLayout-TopBar
  position: fixed
  height: $top-bar-layout-height
  top: 0
  z-index: 9999

.TopBarLayout-Content
  margin-top: $top-bar-layout-height
```

This is just an opinion of course, this could generate a discussion worthy of taking it to The Council ;)