Issue Tracker: Attached image with spaces in name: preview & link fails (BB-7225)

something like this
https://bitbucket.org/hamlinmark1/vcweb/issue-attachment/21/hamlinmark1/vcweb/1357825765.29/21/screen%20grab%20campaign%209.tiff

fails to render causes a broken preview in the issue detail view, and a broken link. if i fiddle with the url i find that the image is available.