add gitlab shell version and updated CHANGELOG

CHANGELOG

@@ -15,6 +15,11 @@ v 5.1.0
   - File history now tracks renames
   - Drop wiki migration tools
   - Drop sqlite migration tools
+  - project tagging
+  - Paginate users in API
+
+v 5.0.1
+  - Fixed issue with gitlab-grit being overrided by grit
 v 5.0.0
   - Replaced gitolite with gitlab-shell

doc/install/installation.md

@@ -99,6 +99,10 @@ GitLab Shell is a ssh access and repository management software developed specia
     git clone https://github.com/gitlabhq/gitlab-shell.git
     cd gitlab-shell
+
+    # switch to right version
+    git checkout v1.2.0
+
     cp config.yml.example config.yml
     # Edit config and replace gitlab_url