Add CHANGELOG entry re: agent rebalancing

CHANGELOG.md

@@ -1,5 +1,17 @@
 ## 0.7.0 (UNRELEASED)
 
+IMPROVEMENTS:
+
+* Consul agents will now periodically reconnect to available Consul servers
+  in order to redistribute their RPC query load.  Consul clients will, by
+  default, attempt to establish a new connection every 120s to 180s unless
+  the size of the cluster is sufficiently large.  The rate at which agents
+  begin to query new servers is proportional to the size of the Consul
+  cluster (servers should never receive more than 64 new connections per
+  second per Consul server as a result of rebalancing).  Clusters in stable
+  environments who use `allow_stale` should see a more even distribution of
+  query load across all of their Consul servers. [GH-1743]
+
 ## 0.6.4 (March 16, 2016)
 
 BACKWARDS INCOMPATIBILITIES: