1.0.4

Upgrading from 1.0.3: There are no backward incompatible changes.

• #133 - fix ErrNotConnected race during Producer connection (thanks @jeddenlea)
• #132 - fix RDY redistribution after backoff with no connections
• #128 - fix backoff stall when using RequeueWithoutBackoff
• #127 - fix handling of connection closing when resuming after backoff (thanks @jnewmano)
• #126 - allow BackoffStrategy to be set via flag (thanks @twmb)
• #125 - add pluggable consumer BackoffStrategy; add full-jitter strategy (thanks @hden)
• #124 - add DialTimeout and LocalAddr config (thanks @yashkin)
• #119 - add Producer.Ping() method (thanks @zulily)
• #122 - refactor log level string handling
• #120 - fix Message data races on responded
• #114 - fix lookupd jitter having no effect (thanks @judwhite)