Allow scripts/styles to be concatenated without minification

[westonruter]

This is the behavior on WordPress.com: scripts and stylesheets are concatenated without any minification. If this was an option, then we could use Dependency Minification to emulate what is being used on WordPress.com, in lieu of https://github.com/Automattic/vip-quickstart/issues/188

• When minification fails due to the JSMin parser not being able to properly process the JS, then fall-back to concatenation only.