add CHANGELOG entry for v1.2.10
add CHANGELOG entry for v1.2.10

songling88/zookeeper,zk-ruby/zookeeper,rickypai/zookeeper,songling88/zookeeper,rickypai/zookeeper,zk-ruby/zookeeper,zk-ruby/zookeeper,rickypai/zookeeper,songling88/zookeeper,songling88/zookeeper,rickypai/zookeeper