circe.el: Typo in the description (also affects package README)
circe-lurker-p: Use the last-active information instead of lurker-p.

Storing 'lurker-p as a user info was quite contrieved, as it was
only ever set with value nil and then queried with a default value
of t to check for lurkerness. With the introduction of 'last-active,
we have a much better metric for that. This simplifies the code in
`circe-lurker-mark-as-active` as well.
lui.el: Fix some compile errors.

The call to `help-xref-interned` was missing the required library,
and `redraw-modeline` is an obsolete alias for `force-mode-line-update`,
which already exists in 23.4, so can be used safely without
backward compatibility issues.

Fixes #45.
circe-duration-string: Rewrite.

The old code was pretty buggy and could return the empty string in
a few corner cases. The new one should be correct.

Added some tests to make sure it does.
test-local.sh: New script to run our tests.

There's a hook to add local Emacs installations for those developers
who have more than one for testing.