change doc link + update install instructions

[marimeireles]

Fixing the docs! Thanks to @jenshnielsen, I always forget they're not pointing to master. I just changed to point to master, cause it's better to have them broken sometimes than not updating them for a year. (Maybe we should automatize this, i don't remember anymore why I didn't do this in the past, but might be a bit of an overhead?)

Thank you @jenshnielsen :)

[github-actions[bot]]

:point_left: Launch a binder notebook on branch marimeireles/ipycytoscape/change-doc-update-readme

[ianhi]

One issue to be fixed on readthedocs is that the default branch of docs still points to latest so if you go to https://ipycytoscape.readthedocs.io/ you end up at latest

[marimeireles]

Oh, thanks for the catch! Will fix :)

[marimeireles]

Done, and also sent an invite for you to have access to this stuff ;) Sorry I forgot Ian.