Move to 4.x notebook as the minimum requirement about dashboards

[parente]

Things known to be broken so far:

• setup.py install fixed: updated and tested
• Paths of config files in makefile fixed: updated and tested
• nbconvert flags (--quiet) fixed: use --log-level
• nbformat.notebooknode.NotebookNode object has no attribute 'layout' when running nbconvert (context is different now?) (bug in master, opened in #92)
• Strange errors before moving to thebe master branch commit w/ 4.0 support, bumped to latest thebe
• IPython.OutputArea no longer defined, fixed: dbl click now adds css img.unconfined rule which we need to reset to prevent double click overflowing grid cell
• Have to wait for kernel_ready.Kernel before executing code now else execute requests are dropped (used to queue?) (bug in master, fixed in PR #85)
• demo changes (ipywidgets JS paths, ipywidgets top level package, traitlets top level package) fixed: scotch notebook, all test/* notebooks, pending decl widget bump to 4.x compat to test all others
• focus rects around cells in deployed dashboard fixed: transparent border for selected cells

[parente]

All known bugs handled. Putting in stasis pending decl widget update to 4.x too.

[parente]

Merged into master on Friday after lots of manual demo testing plus all green on Travis.