Safari bug: Input cut off in multiselect
Version: Safari 11.0.3
To reproduce, select one option and begin typing to select a second.
The beginning of input text is cut off.
See example from your demo site

I was able to reproduce it. I'm not sure if I will have time to fix it soon, so if anyone wants to give it a try I should have time to review and merge it.
When someone get around to fixing this, there is a similar bug in IE11 where text is either off center, or cut off (also occurs on the demo page, for multi select)
Typing in the box normally, produces off center text

Copy & paste text into the box then centers the text, but it is cut off (notice that the cross button at the right is also way off center). Note, if you then edit the text after copy/paste, it reverts to the off center position

Hopefully IE11 dies off soon (:
It doesn't matter a huge deal just for basic searches, but when using the ember-power-select-multiple-create plugin to create new entries, it's kind of a pain