Prevent calling reply func twice on killed sockets.
Experimental SASL support.
Lowercase errors and panics.
Document new Dial options.
In public docs: master => primary; slave => secondary
Get rid of against in the documentation. What a bad word.
Trivial tweaks in package-level docs.
Small comment fixes, by Dmitry Chestnykh.
Break out of Iter.Next if getMore failed.
Tweak tests for 2.6.
Don't burn CPU if no masters are found and FailFast is set.