Fix outstanding broken links

[philippjfr]

Here is a Google Sheet with remaining broken links. We should fix these soon.

[jlstevens]

#1618 is probably in the list but referencing the issue to make sure.

[jlstevens]

PR #2509 fixed a bunch of links for 1.10.

I'm assigning this issue to 1.10.x as a reminder to run a link checker again after the website is updated to catch any other (or new) broken links that aren't fixed by that PR.

[bewt85]

Hi, I don't think you have these which I found in the showcase tutorial
http://holoviews.org/Tutorials/Introduction.ipynb
http://holoviews.org/Tutorials/Exploring_Data.ipynb
http://holoviews.org/Tutorials/Options.ipynb
http://holoviews.org/Tutorials/Elements.ipynb
http://holoviews.org/Tutorials/Containers.ipynb

and
https://ioam.github.io/param/ in http://holoviews.org/Tutorials/Introduction.html

Thanks for making a great tool.

[philippjfr]

Closing this since the list is outdated.