Added windows usage remarks

Author: akaustel

Readme.md

@@ -47,10 +47,22 @@ setInterval(function(){
 
  The __DEBUG__ environment variable is then used to enable these based on space or comma-delimited names. Here are some examples:
 
+### OSX and Linux usage
+
   ![debug http and worker](http://f.cl.ly/items/18471z1H402O24072r1J/Screenshot.png)
 
   ![debug worker](http://f.cl.ly/items/1X413v1a3M0d3C2c1E0i/Screenshot.png)
 
+### Windows usage
+
+ On Windows the environment variable is set using the `set` command. 
+ 
+ ```cmd
+ set DEBUG=*,-not_this
+ ```
+
+The run the program to be debugged as ususal.
+
 ## Millisecond diff
 
   When actively developing an application it can be useful to see when the time spent between one `debug()` call and the next. Suppose for example you invoke `debug()` before requesting a resource, and after as well, the "+NNNms" will show you how much time was spent between calls.