Improve grammar in CI documentation for build vars

doc/ci/variables/README.md

@@ -70,17 +70,20 @@ These variables can be later used in all executed commands and scripts.
 
 The YAML-defined variables are also set to all created service containers, thus allowing to fine tune them.
 
-Variables can be defined on a global level, but also on a job level.
+Variables can be defined at a global level, but also at a job level.
 
 More information about Docker integration can be found in [Using Docker Images](../docker/using_docker_images.md).
 
 ### User-defined variables (Secure Variables)
 **This feature requires GitLab Runner 0.4.0 or higher**
 
-GitLab CI allows you to define per-project **Secure Variables** that are set in build environment.
+GitLab CI allows you to define per-project **Secure Variables** that are set in
+the build environment.
 The secure variables are stored out of the repository (the `.gitlab-ci.yml`).
-The variables are securely passed to GitLab Runner and are available in build environment.
-It's desired method to use them for storing passwords, secret keys or whatever you want.
+The variables are securely passed to GitLab Runner and are available in the
+build environment.
+It's desired method to use them for storing passwords, secret keys or whatever
+you want.
 
 **The value of the variable can be shown in build log if explicitly asked to do so.**
 If your project is public or internal you can make the builds private.