[Docs] Fix breadcrumb trail

[dragoonis]

Go here: http://dev.ppi.io/docs/getting_started.html

There's a 'back' url that shouldn't be there, to 'the book'.

We need to remove this somehow from the ppi_frame theme's tree.

See here, this is how we output the prev/next stuff: https://github.com/dragoonis/ppi-docs/blob/master/_themes/ppi_frame/layout.html#L6

[dragoonis]

@noisebleed, is this something you know the answer to?

I'd like to go live with the new docs ASAP so this is kind of more important then any framework task right now.

[dragoonis]

Done.