Switch to better jQuery modal plugin

[siamkreative]

Our current modal plugin, EasyModal is outdated and multiple users pointed out that the z-index calculation often fails, including @tevyaw.

We need a modal that is robust, and that can eventually support custom animations using animate.css or else.

• Remodal: https://github.com/VodkaBears/Remodal/
• Magnific-Popup: https://github.com/dimsemenov/Magnific-Popup

[siamkreative]

An accessible dialog window library for all humans. http://humaan.com/modaal/