fix(README): fixup a grammar bug

README.md

@@ -9,7 +9,7 @@ A highly-available key value store for shared configuration and service discover
 * Fast: benchmarked 1000s of writes/s per instance
 * Reliable: Properly distributed using Raft
 
-Etcd is written in Go and uses the [raft][raft] consensus algorithm to manage a highly availably replicated log.
+Etcd is written in Go and uses the [raft][raft] consensus algorithm to manage a highly-available replicated log.
 
 See [go-etcd][go-etcd] for a native Go client. Or feel free to just use curl, as in the examples below.