Add support for relative url to GitLab.GfmAutoComplete.Emoji.assetBase

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/views/layouts/_init_auto_complete.html.haml

 :javascript
   GitLab.GfmAutoComplete.dataSource = "#{autocomplete_sources_project_path(@project)}"
-  GitLab.GfmAutoComplete.Emoji.assetBase = '/assets/emoji'
+  GitLab.GfmAutoComplete.Emoji.assetBase = "#{Gitlab.config.gitlab.relative_url_root + '/assets/emoji'}"
   GitLab.GfmAutoComplete.setup();