Add userlib tests

Document userlib in readme
extend example configuration to include userlib

src/stl/control.rs

@@ -31,7 +31,6 @@ example: (if my-state-switch
 
 pub fn if_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, String> {
     let cond: bool;
-    println!("Y: {}", *ast.car);
     match *ast.car {
         Ctr::Seg(ref cond_form) => {
             if let Ctr::Bool(cond_from_eval) = *eval(cond_form, syms)? {