Adds missing entry to Readme about broken module compatibility.

* see 3f1e064c91474ff9bd45ea39b11bc7bd564125c6.

diff --git a/README.md b/README.md
index ac506be..6591391 100644 (file)
--- a/README.md
+++ b/README.md
@@ -31,6 +31,7 @@ npm install clean-css
 #### Module interface
 
 * `noAdvanced` became `advanced` - make sure to reverse the value;
+* no longer possible to use `CleanCSS` as a function as `new CleanCSS` is always required;
 
 ### How to upgrade clean-css from 1.x to 2.x?