Add URL router for deeplinking, start presenting, run-all

[bollwyvl]

As a user, I want to be able to bookmark a particular slide in a presentation, and have it

• start presenting
• run all the cells?
• immediately go to the slide I link

It should be possible to deep link to a particular slide, either:

• explicitly: #slide/u-u-i-d
• loosely: #slide/0
• named: #slide/title-slide (most work, but probably the best, long-term)

Since many rich presentations may require execution (e.g. connect widgets), and should be run-allable, we'd need some way to specify this:

http://localhost:8888/notebooks/presentation.ipynb#!slide/title-slide

This would allow a user to:

• link to a particular slide from another slide, creating a "table of contents" for a long presentation
• share a link to a meaningful place

This should all work for the static HTML case, as well as the interactive case... so obviously run-all wouldn't matter.