remove nats resubscribe/reconnect logic

The on_reconnect callback is actually called when a reconnect ATTEMPT is
made, not when it reconnects. The NATS client resubscribes for us
already, so we don't need to use it anyway.

[#54338464]

Signed-off-by: Glenn Oppegard <goppegard@pivotallabs.com>
bump nats dependency to 0.5.x for cluster support

Signed-off-by: Eric Malm <emalm@pivotallabs.com>
accept :servers and :uris for nats server config

Signed-off-by: Eric Malm <emalm@pivotallabs.com>
bump to 0.2.0

Signed-off-by: Eric Malm <emalm@pivotallabs.com>
bump Gemfile.lock

Signed-off-by: Eric Malm <emalm@pivotallabs.com>
configure nats client to not shuffle servers

This works around a NATS ruby library bug that led to the client
dropping servers from its connection pool.

Signed-off-by: Eric Malm <emalm@pivotallabs.com>