resolve problems from deps upgrade

- downgrade reqwest to 0.11.27
  - fixes problems with missmatched transitive dependencies between it and warp, mainly http
- replace deprecated ripemd160 with ripemd (as specified in the formers readme)
- indexmap: replace deprecated remove with functionally identical swap_remove

src/arithmetic.rs

@@ -18,7 +18,7 @@ use crate::machine::machine_errors::*;
 use dashu::base::Abs;
 use dashu::base::BitTest;
 use num_order::NumOrd;
-use ordered_float::*;
+use ordered_float::{Float, OrderedFloat};
 
 use std::cell::Cell;
 use std::cmp::{max, min, Ordering};