Version history notes collapsible

• Follows https://gitlab.com/gitlab-com/gitlab-docs/merge_requests/465
• Closes https://gitlab.com/gitlab-com/gitlab-docs/issues/380

To-dos

• Tweak filter for adding a Bootstrap collapse link.
• Style it.
• Once https://gitlab.com/gitlab-com/gitlab-docs/merge_requests/465 is merged, pull master.
• BE: Make it with different div ids so that multiple buttons on the same page will work.
• Get/incorporate UX/FE feedback.

Proposal

Single-line	Multi-line
Review App	Review App
v2	v2
v1	v1