None of my Add-ons install properly

Anytime I install anyone else's add-ons, it works fine. When I test out MY add-ons, it just goes to the part that says 'Installing..' like any other, but never installs. I think this is totally unfair and needs to be fixed. I want to test the add-ons I made so I can find errors to fix and I want to be sure that others can use it too. An example can be downloaded [here|http://www.mediafire.com/file/bud74j04yrti42z/wither%20villagers%201.4.mcpack].