made the switch to using bracket-lib directly, instead of rltk wrapper

this should solve the build issues; it makes using the non-crashing github build a lot easier, because it lets the explicit rltk dependency be removed.

src/map_builders/forest.rs

@@ -11,12 +11,12 @@ use super::{
     YStart,
     Foliage,
 };
-use rltk::prelude::*;
+use bracket_lib::prelude::*;
 use crate::data::names::*;
 
 pub fn forest_builder(
     new_id: i32,
-    _rng: &mut rltk::RandomNumberGenerator,
+    _rng: &mut RandomNumberGenerator,
     width: i32,
     height: i32,
     difficulty: i32,