Dash bio styling

[smallstepman]

• shorten URLs with git.io
• get rid of double new lines
• fix: use hide_code=true instead of no_display=true to actually hide cells with code which renders iframes

[nicolaskruchten]

Could you please target all the documentation-related PRs to the doc-prod branch rather than master? They're not auto-deployed from master and we shouldn't be merging master into doc-prod except when doing releases (i.e. every 6-8 weeks)

cc @HammadTheOne @olayway