Production as default, development/demo configurable

[ausi]

With the next major version we should turn the postcss configuration option on by default or rename it to preprocess and invert the value.

The goal of this change is to make the use in production more straight forward and that the default case is the one with better performance.

Maybe we should also add a loadCorsStylesheets configuration option that defaults to false, so that we don’t fetch any stylesheets by default (in modern browsers). Legacy browsers would still need an ajax call for stylesheets that have the crossorigin attribute set.

[ausi]

Implemented in version 0.4.0.