isInline undefined on root Nav

[chrisvxd]

When rendering a root nav, isInline is undefined. This is confusing.

Since root is a special case, we should either:

1. Set both isInline AND isStack to true or
2. Add another prop called isRoot

In the meantime, users can get around this by checking route === 'root'

[chrisvxd]

isInRoute is also undefined in root Nav