Update v1.5.2 README (#366)

* add release note(1.5.0)

* update docs

* update docs

* underline Bert Service for v1.5.0

* release v1.5.1

* upadte docs

* release v1.5.2

docs/release.md

 # 更新历史
 
+## `v1.5.2`
+
+* 优化pyramidbox_lite_server_mask、pyramidbox_lite_mobile_mask模型的服务化部署性能
 
 ## `v1.5.1`
 

paddlehub/version.py

@@ -13,5 +13,5 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 """ PaddleHub version string """
-hub_version = "1.5.1"
+hub_version = "1.5.2"
 module_proto_version = "1.0.0"