Change use readthedocs *stable* link
Change use readthedocs *stable* link

Also remove the explicit version in the readme. The reason
being that this seems like a likely thing to be forgotten to be
updated when making a new release.

jupyter-widgets/ipywidgets,ipython/ipywidgets,jupyter-widgets/ipywidgets,ipython/ipywidgets,jupyter-widgets/ipywidgets,jupyter-widgets/ipywidgets,ipython/ipywidgets,ipython/ipywidgets,ipython/ipywidgets