Fix change log format

Author: yangaws

CHANGELOG.rst

@@ -8,25 +8,25 @@ CHANGELOG
 * bug-fix: AmazonEstimators: fix valid range of hyper-parameter 'loss' in linear learner
 
 1.2.0
-========
+=====
 
 * feature: Add Support for Local Mode
 * feature: Estimators: add support for TensorFlow 1.6.0
 * feature: Estimators: add support for MXNet 1.1.0
 * feature: Frameworks: Use more idiomatic ECR repository naming scheme
 
 1.1.3
-========
+=====
 
 * bug-fix: TensorFlow: Display updated data correctly for TensorBoard launched from ``run_tensorboard_locally=True``
 * feature: Tests: create configurable ``sagemaker_session`` pytest fixture for all integration tests
-* bug-fix: AmazonEstimators: fix inaccurate hyper-parameters in kmeans, pca and linear learner
-* feature: Add new hyperparameters for linear learner.
+* bug-fix: Estimators: fix inaccurate hyper-parameters in kmeans, pca and linear learner
+* feature: Estimators: Add new hyperparameters for linear learner.
 
 1.1.2
 =====
 
-* bug-fix: AmazonEstimators: do not call create bucket if data location is provided
+* bug-fix: Estimators: do not call create bucket if data location is provided
 
 1.1.1
 =====