Fixed #65. When scan duration is negative, use timenow to find the elapse.

Eventually we want to make it real time so that time be incrementing as we wait.
Fixed #66. If scan hasn't started, show '---' instead of 44 years ago or never.

Never as a default value sounds weird, so I proposed the switch to '---'.
Since the original implementation append a time elapse filter with ()
in the template, to make use of the changes in the filter
``scan_datetime`` without hardcoding the ``()`` in the Javascript (that's a
presentation logic), I use ``ng-show``.
Merge pull request #73 from yeukhon/moment-datetime

Fixed #65. When scan duration is negative, use timenow to find the elaps...
Merge pull request #74 from yeukhon/issue66

Fixed #66. If scan hasn't started, show '---' instead of 44 years ago or...
Fixed #75. Add Classification to issue page.
Don't show extra info if there is none.

It looks ugly when we have an empty td whe extra info
is not provided.
Fixed #80. Exposes attack-releated detail in issue page.
Fixed #81. Don't display classification unless one of the ids is present.

Ideally we want to display that (even as Unknown), but the wording and
appearance wise, I think this row should be hidden IF neither ids are present.
Merge pull request #79 from yeukhon/enhance-output

Fixed #75. Fixed #80. Fixed #81. Expose attack and reference details.