Fix warnings for 'is rw' on private attributes

... by making the attributes public, like all the others in
Net::IRC::Bot.
Improve debugging of raw IRC protocol traffic

Also allow commands that carry private information (such as passwords)
to output scrubbed debugging info instead of raw traffic.
Scrub password from NS IDENTIFY debug info
Factor out some text utilities into a separate module

_s() for pluralizing and friendly-duration() for converting durations
in seconds to appropriately larger units for display
Add a per-event cache so modules can avoid repeated work
Add a role for simplifying command-handler modules
Use CommandHandler role in Tell module

Also fix an over-simplistic nick token and add a usage message.
Add a module implementing the seen command
Add some ACME classes to show use of prefix for commands
Merge pull request #6 from japhb/master

Debugging, refactoring, and some new functionality (including a CommandHandler role and the seen command)