Triggering goal in JS results in error if Django APPEND_SLASH setting is True

[dboris]

RuntimeError: You called this URL via POST, but the URL doesn't end in a slash and you have APPEND_SLASH set. Django can't redirect to the slash URL while maintaining POST data. Change your form to point to /experiments/goal/upgrade_banner_click/ (note the trailing slash), or set APPEND_SLASH=False in your Django settings.
[07-21 23:28:59] ERROR "POST /experiments/goal/upgrade_banner_click HTTP/1.1" 500 52303

[Vadim-Karpenko]

i create issue to fix that, you can manually copy code from experiments.js and make your own js file, and insert my fix #168