Install an error template for the dashboard.

This isn't all that informative of an error message, but it does let you
know that (A) your action was acknowledged, and (B) it resulted in an
error.  Previously, (A) wasn't even clear.
Dashboard: GET /history will always give you an answer.

If no records exist for the given URL, we now return [] with status code
200.  This is probably a better interpretation of what we had before:
we're saying "I acknowledge the existence of your resource (a URL) and I
have zero history records that relate to it".
Use Trollop for job option parsing; add --js.
Pipeline and bot support for wpull's PhantomJS mode.
Don't generate page snapshots in PhantomJS mode.
--js -> --phantomjs.

The latter is longer, but seems to be more obvious.
Require that pipeline nodes have PhantomJS.

1.9.0 is latest stable.
Require wpull 0.33.1.

0.33.1 contains a fix for https://github.com/chfoo/wpull/issues/120,
which needed to be resolved for ArchiveBot use.