Resolve "Graphs and Wiki subnav"

Styles sub nav in `Wiki` and `Graphs`

Closes #18533

![Screen_Shot_2016-06-15_at_9.32.43_AM](/uploads/111dae6e1b9c7d8038ac88b9be6f76a2/Screen_Shot_2016-06-15_at_9.32.43_AM.png)

cc @dzaporozhets

See merge request !4678