Update selectize.js to 0.15.2

[php-coder]

Changelogs:

• https://github.com/selectize/selectize.js/releases/tag/v0.13.6
• https://github.com/selectize/selectize.js/releases/tag/v0.14.0
• https://github.com/selectize/selectize.js/releases/tag/v0.15.0
• https://github.com/selectize/selectize.js/releases/tag/v0.15.1
• https://github.com/selectize/selectize.js/releases/tag/v0.15.2