Point release fixing an issue with Jupyter rendering order.

Previously, when a Jupyter notebook containing Scenepic cells was
loaded after having been saved, the outputs would appear out
of order within the notebook. Also, the full library was written into
each cell, resulting in a lot of duplicate Javascript for notebooks
which included heavy use of the library. The new solution uses a few
elements to avoid this:

• The library is written as an external script file in the same directory
  as the notebook. This has the advantage of making debugging the
  Typescript library easier (this is a return to previous functionality).
• The library is loaded once via a single script tag
• Each cell is assigned a unique ID that is used by scenepic to target it
• When reloading a saved notebook, order is preserved due to the use of
  the unique ids.