Use redis_options only if we're creating a Redis object ourselves

There's no point in setting a default reconnect value in the
redis_options hash if we're using an already existing Redis
object (potentially constucted with a different reconnect
value).
Fix a couple of typos
help info, forgotten command
s/it's/its/ where applicable
Fix POD typo in method name
Fix a couple of typos in the documentation
Warn on failed lua calls to requeue_failed
New option NoSigHandlers for the consume() method

This option will disable the installation of signal handlers for INT
and TERM. Moreover, the signals handlers now installed by default
will call whatever user-defined previous handler that might have
been installed previously.
Cosmetics
More cosmetics and little Perl-sanity fixes
Add TODO comment with a potential improvement/optimization
More Cosmetics
Nuke trialing whitespace
Limit scope of variables
Cosmetics
Yet more cosmetics
Documentation improvements
Implement non-blocking claim_item_nonblocking

And document the normal claim_item().
Reverse Changelog order: newest first
Version bump, changelog