Merge pull request #4846 from jonboulle/master

docs: "master election" -> "leader election"

Documentation/api.md

@@ -80,7 +80,7 @@ X-Raft-Term: 1
 
 * `X-Etcd-Index` is the current etcd index as explained above. When request is a watch on key space, `X-Etcd-Index` is the current etcd index when the watch starts, which means that the watched event may happen after `X-Etcd-Index`.
 * `X-Raft-Index` is similar to the etcd index but is for the underlying raft protocol.
-* `X-Raft-Term` is an integer that will increase whenever an etcd master election happens in the cluster. If this number is increasing rapidly, you may need to tune the election timeout. See the [tuning][tuning] section for details.
+* `X-Raft-Term` is an integer that will increase whenever an etcd leader election happens in the cluster. If this number is increasing rapidly, you may need to tune the election timeout. See the [tuning][tuning] section for details.
 
 ### Get the value of a key