Examples section, binder prep, & GIF-stack example from webinar

[gjoseph92]

• Create an examples subdirectory for example notebooks
• Examples sub-heading in documentation
• Get everything set up for Binder. It works—but you can't connect to a Coiled cluster, because Binder blocks 8787 (and most other ports): https requests from Sparql kernel jupyterhub/mybinder.org-deploy#694 (comment). Once Coiled supports using other ports, I'll turn Binder on.
• Add a Cape Cod Landsat-8 GIF example
• Driveby: update some deps