Make the side bar about in-document navigation by removing the duplicated h1


![docs_screenshot](https://cloud.githubusercontent.com/assets/28492/4195590/05d467ec-37c3-11e4-99a7-91661277a9b9.png)


Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)

for @fredlf  :)