Company Logo is not centered
Created by: spuder
Description: If you add a company logo to the config/gitlab.yaml file, the logo will align left
Observed Behavior: The logo will align left.
Expected Behavior: The logo should align center.
Steps to reproduce: Add the following the config/gitlab.yml
## Text under sign-in page (Markdown enabled)
sign_in_text: |

[Learn more about CompanyName](http://www.companydomain.com/)
Work around: Make sure the logo is exactly 302 px wide