Added relative path for asset in image page part

Otherwise it does not work, if kuma is installed to a relative folder.
Update view.html.twig

Added host and path information
Merge pull request #24 from DracoBlue/master

Add absolute path for image-pp and download-pp
Merge branch 'master' into 2.3

* master:
  Update view.html.twig
  Added relative path for asset in image page part
travis.yml for stable branch