Fix scheduled builds.

When trying to run scheduled builds on 4.0 the cron job fails with the following error message:

```
/bin/bash: bundle: command not found
```

This is caused by bundle not being in `PATH` when running `bundle exec rake schedule_builds` from cron.

This PR fixes the docs so the gitlab_ci user we create can have a modifiable environment where we can add `bundler` to `PATH` by modifying `.profile` or similar depending on which type of system the user is on.

I also removed two occurrences of puts that would cause the cronjob to send email to the gitlab_ci user.