Version 0.2.2

Three minor improvements:

1. We now track open viewers for you in case you forget to assign them to a variable:

   import octarine as oc 
   oc.Viewer()   # whoops, forgot to assign
   v = oc.viewers[0]  # phew!

   Closing via Viewer.close() removes the reference to avoid preventing garbage collection.
2. Viewer.show() will now just simply display the jupyter_rbf widget when used in Jupyter (eliminates the previous extra step)
3. Viewer.add_lines: the linestyle parameter now also accepts matplotlib-like styles such as -- or :