Speed up rendering when there are lot of select choen

[dhwang]

A simple change to speed up rendering when there are lots of select drop down to conver to select-chosen

Summary

Provide a general description of the code changes in your pull request.

Please double-check that:

• [ ] All changes were made in CoffeeScript files, not JavaScript files.
• [ ] You used Grunt to build the JavaScript files and tested them locally.
• [ ] You've updated both the jQuery and Prototype versions.
• [ ] You haven't manually updated the version number in package.json.
• [ ] If necessary, you've updated the documentation.

See the Pull Requests section of our Contributing Guidelines for more details.

References

If your pull request is in reference to one or more open GitHub issues, please mention them here to keep the conversations linked together.