refs TryGhost/Ghost#7427
Removes `-contributors.hbs` and `public/assets/img/contributors` from `.gitignore`.
Removes `buildAboutPage` from `grunt init` task.
Updates `contributors.hbs` and adds images for each contributor.
Changes the `max-width` of `.gh-credits` wrapper to be 700px instead of 650px, so we'll fit them all in two rows.
no issue
- as it's more likely that Ghost-Admin will be checked out separately it makes sense that it has its own `.gitignore` and `.editorconfig` that match the core repository
- added grunt-bg-shell
- reorganized asset tasks into one location
- turn off ember-cli analytics
- remove app/config-dev and config-prod
- remove qunit from bower.json
- remove express from package.json
