Make it clearer that groupcache is distributed

README.md

@@ -2,8 +2,8 @@
 
 ## Summary
 
-groupcache is a caching and cache-filling library, intended as a
-replacement for memcached in many cases.
+groupcache is a distributed caching and cache-filling library, intended as a
+replacement for a pool of memcached nodes in many cases.
 
 For API docs and examples, see http:https://godoc.org/github.com/golang/groupcache
 
@@ -17,7 +17,8 @@ For API docs and examples, see http:https://godoc.org/github.com/golang/groupcache
 
  * does not require running a separate set of servers, thus massively
  reducing deployment/configuration pain. groupcache is a client
- library as well as a server. It connects to its own peers.
+ library as well as a server. It connects to its own peers, forming
+ a distributed cache.
 
  * comes with a cache filling mechanism. Whereas memcached just says
  "Sorry, cache miss", often resulting in a thundering herd of