Phriction - kill tabs

Summary:
...except that pesky help tab which remains.

Pertinent bits here...

• move "History" into button "View History" that is grey and next to "Edit Page"
• for history page, add breadcrumb similar to the one on "diff" page. This

unifies the experiencing on history <=> diffs as well as gives the user a link
back to the document, which was a tab on the History page before this diff.

Thoughts for next time...

• I'd like to further unify the breadcrumbs between "View" and "History / Diff".
• The "Document Index" is pretty sweet and feels a bit buried. I wonder if

unifying breadcrumbs is the key here?

Test Plan: clicked around phriction. viewed a document, viewed its history.
verified links in breadcrumbs were correct

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, epriestley

Maniphest Tasks: T631

Differential Revision: 1221