Remove codeclimate init call in documentation

See the general Documentation guidelines http://docs.gitlab.com/ce/development/doc_styleguide.html

What does this MR do?

Codeclimate has updated, breaking the build for anyone following these instructions. The init subcommand no longer exists. This changes the recommended way of using codeclimate to address this and to include an allow_failure: true to the build step.

Moving docs to a new location?

See the guidelines: http://docs.gitlab.com/ce/development/doc_styleguide.html#changing-document-location

• Make sure the old link is not removed and has its contents replaced with a link to the new location.
• Make sure internal links pointing to the document in question are not broken.
• Search and replace any links referring to old docs in GitLab Rails app, specifically under the app/views/ directory.
• If working on CE, submit an MR to EE with the changes as well.