I'm getting the error
Selectize: Dependency MicroPlugin is missing
Make sure you either: (1) are using the "standalone" version of Selectize, or (2) require MicroPlugin before you load Selectize.
application.js:
//= require jquery
//= require jquery_ujs
//= require selectize
//= require turbolinks
//= require bootstrap-sprockets
//= require jquery.validate
//= require jquery.validate.additional-methods
//= require_tree .
I changed my application.js to
//= require selectize/standalone/selectize
I figured it out by looking at the load paths
~/.rvm/gems/ruby-2.3.1/gems/rails-assets-selectize-0.12.3/app/assets/javascripts
and found standalone was in /selectize/standalone/selectize.js
I knew to look there by looking at their examples.