Issue 43 make sort(reverse=True) work

There were two possible approaches to making key=value parameters
work and I took what I saw as the safe impact with the most limited impact.

I also tried code in function.js that automatically added the
co_varnames to all functions defined using Sk.builtin.func as follows:

  if ( code )
 {
     funStr = code.toString();
     parms= funStr.slice(funStr.indexOf('(')+1, funStr.indexOf(')')).match(/([^\s,]+)/g);
     if ( parms.length > 0 )
     {
         this.func_code['co_varnames']=parms;
     }
 }

This code worked for sort(reverse=True), but lots of code started to fail in
the unit tests having to do with parameter passing and Python defined functions.
It would be good in the above code to only trigger on native JS library functions.