Fix sagemaker release version to 1.2.0 in doc and readme

Author: yangaws

README.rst

@@ -47,7 +47,7 @@ You can install from source by cloning this repository and issuing a pip install
 
     git clone https://github.com/aws/sagemaker-python-sdk.git
     python setup.py sdist
-    pip install dist/sagemaker-1.1.3.tar.gz
+    pip install dist/sagemaker-1.2.0.tar.gz
 
 Supported Python versions
 ~~~~~~~~~~~~~~~~~~~~~~~~~

doc/conf.py

@@ -18,7 +18,7 @@ def __getattr__(cls, name):
                 'tensorflow.python.framework', 'tensorflow_serving', 'tensorflow_serving.apis']
 sys.modules.update((mod_name, Mock()) for mod_name in MOCK_MODULES)
 
-version = '1.1.3'
+version = '1.2.0'
 project = u'sagemaker'
 
 # Add any Sphinx extension module names here, as strings. They can be extensions