Suggested navigation improvements

[DartBot]

From @bwilkerson on September 16, 2014 21:36:13

I went to https://pub.dartlang.org/packages/analyzer and clicked on the "Versions" tab. There is a column for "Documentation" and I was curious to see what the icons were linked to. They're not linked to anything because there is no documentation (I'm not sure why). It would be nice if the absence of this file could be detected and the icon grayed out instead of producing a 404.

I then clicked on the back button to go back to the version list, but it reset the page state to show me the README.md tab instead. It would be nice if it remembered the previous state.

Original issue: http://code.google.com/p/dart/issues/detail?id=20969

[srawlins]

Looks like a dup of #241. Plus the bit on remembering the tab.

[nex3]

I went to https://pub.dartlang.org/packages/analyzer and clicked on the "Versions" tab. There is a column for "Documentation" and I was curious to see what the icons were linked to. They're not linked to anything because there is no documentation (I'm not sure why). It would be nice if the absence of this file could be detected and the icon grayed out instead of producing a 404.

I'm not sure why these old docs haven't built, but I think this is more of an issue of dartdocs.org not giving a good error message.