Change "master/slave" terminology to "primary/replica"

[marcy-buccellato]

Hi @peterdemin Love this helpful, simple utility - thanks for this! Just wondering about changing the terminology. As you know, Github and other tech orgs are moving away from the offensive "master/slave" terminology.

Should be a pretty simple find/replace operation. You open to my creating a PR for this change? Any other suggestions for replacement terms?

[peterdemin]

Hi @marcy-buccellato, I haven't used this project for 6+ years. I'm okay with you working on such PR. But please keep backward compatibility - rename "slave" to "replica", but add a "slave" alias pointing to "replica".
So that existing projects, that use "master/slave" API keep working.