Merge branch 'link-to-installation-doc' into 'master'

Link to installation doc

doc/install/installation.md

 # Select Version to Install
-Make sure you view this installation guide from the branch (version) of GitLab you would like to install. In most cases
+Make sure you view [this installation guide](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/install/installation.md) from the branch (version) of GitLab you would like to install. In most cases
 this should be the highest numbered stable branch (example shown below).
 
 ![capture](http://i.imgur.com/d2AlIVj.png)
 
-If this is unclear check the [GitLab Blog](https://www.gitlab.com/blog/) for installation guide links by version.
+If the highest number stable branch is unclear please check the [GitLab Blog](https://www.gitlab.com/blog/) for installation guide links by version.
 
 # Important notes