Moving examples to the top level.
First go and reorganizing the examples.
Updating MANIFEST.in for new examples location.
More changes to example notebooks.
Finishing the display example notebooks.
Adding Cell Magics notebook.
Simple changes to make example notebooks Python 3 compatible
Fix 'Custom Display Logic' example notebook for Python 3
More changes to example notebooks for Python 3 compatibility
Adding FileLink example in the right new place.
Updating docs to reflect new examples.

* Changed literalinclude paths to point to /examples.
* Removed parallel options demo from parallel_demos.txt as it
  is now a notebook. Eventually we will find a way to integrate
  notebooks with the sphinx docs, but that is beyond the scope of
  this branch.
Updating a few example notebooks to v3.
Merge pull request #2537 from ellisonbg/examples

Organize example notebooks

- Some refactor and reorganization of notebooks
- examples moved to top-level examples dir, out of docs
- py3compat along the way

closes #2622