Bouncing to 404 page on a bad tree-browse request

This is a URL whose first argument (beyond the optional app-name
'opentree') is invalid. That is, it's neither a viewer name (eg,
'argus') nor a proper destination (eg, 'otol.draft.22@123')
Merge pull request #101 from OpenTreeOfLife/simple-curation-app

Bouncing to 404 page on a bad tree-browse request