store timestamps in irc logs in iso8601 (utc)

The previous behavior of storing timestamps in the server's local
timezone without any TZ info is crazy sauce. This maintains backwards
compatibility for those logs, however.

refs #17
add timezone support for backlog

if you have a GeoIP.dat (preferably the city one) as described in
the geoip gem's documentation, it will even autodetect
Merge pull request #40 from ccutrer/dev/tz

add timezone support for backlog
Merge pull request #41 from ccutrer/dev/single_who

only send replies to WHO to the client that requested them
bump version
add rake to dev gemfile
replay messages sent from one client immediately to other connected clients

fixes #35