Added USERLIB with prepend and set.

Added a q shortcut to quote
get-doc and set-doc no longer conditionally evaluate args
Fixed bug in let, documented potential performance improvements
upped default history to 5k lines

src/bin/main.rs

@@ -78,7 +78,7 @@ fn main() -> ! {
     let mut rl = Reedline::create();
     let maybe_hist: Box<FileBackedHistory>;
     if !hist_file_name.is_empty() {
-        maybe_hist = Box::new(FileBackedHistory::with_file(5, hist_file_name.into())
+        maybe_hist = Box::new(FileBackedHistory::with_file(5000, hist_file_name.into())
                               .expect("error reading history!"));
             rl = rl.with_history(maybe_hist);
     }