Update documents according to:

https://gitlab.com/gitlab-org/release-tools/blob/master/doc/release-candidates.md#step-1-update-the-installation-from-source-guide

In step 1 and step 2

doc/install/installation.md

@@ -289,9 +289,9 @@ sudo usermod -aG redis git
 ### Clone the Source
     # Clone GitLab repository
-    sudo -u git -H git clone https://gitlab.com/gitlab-org/gitlab-ce.git -b 9-0-stable gitlab
-**Note:** You can change `9-0-stable` to `master` if you want the *bleeding edge* version, but never install master on a production server!
+    sudo -u git -H git clone https://gitlab.com/gitlab-org/gitlab-ce.git -b 9-1-stable gitlab
+**Note:** You can change `9-1-stable` to `master` if you want the *bleeding edge* version, but never install master on a production server!
 ### Configure It
@@ -475,7 +475,7 @@ with setting up Gitaly until you upgrade to GitLab 9.2 or later.
     sudo -u git cp config.toml.example config.toml
     # If you are using non-default settings you need to update config.toml
     sudo -u git -H editor config.toml
-    
+
     # Enable Gitaly in the init script
     echo 'gitaly_enabled=true' | sudo tee -a /etc/default/gitlab

doc/update/9.0-to-9.1.md

 # From 9.0 to 9.1
-** TODO: **
-
-# TODO clean out 9.0-specific stuff
-
 Make sure you view this update guide from the tag (version) of GitLab you would
 like to install. In most cases this should be the highest numbered production
 tag (without rc in it). You can select the tag in the version dropdown at the