wait for pending renders of the same URL

reduces load when one URL is requested many times
move pending set after cache miss
Merge pull request #224 from minrk/render-pending

wait for pending renders of the same URL
[print] hide menubar and footer

see http://getbootstrap.com/css/#responsive-utilities-print
don't quote external links in tree view

they are already escaped
make breadcrumbs a macro
Merge pull request #227 from minrk/fix-external-links

don't quote external links in tree view
add breadcrumbs method
add breadcrumbs to notebook view
fix link to repo listing in tree view
remove open in nbviewer confusing link
Merge pull request #229 from Carreau/no-open-in

remove open in nbviewer confusing link
Merge pull request #225 from pierriko/feature-print

[print] hide menubar and footer
Merge pull request #228 from minrk/breadcrumbs

add breadcrumbs to notebook page
Calling of SlidesExporter, change of notebook template, add of reveal.js 2.6.0.
Changed missing static url.
Added zoom = 1 to the slideshow to scale properly inside the container. Inherit the height of the container to show at full height.
Auto zoom on because is no longer necessary after inherit of height container and to support auto scale of slideshow.
Changed fontsize, line height and avoid display of footer.
Changed the index template to fit slides viewer and not nbviewer.