linear search instead of binary search, unwrap() instead of expect()

Linear search should be more performant than binary search for all
reasonable use cases (never more than 30 dimensions).
Removed the expect() because it will add dedicated panic and printing
code that should never execute.

Author: vbarrielle

src/dimension.rs

@@ -27,11 +27,12 @@ fn fastest_varying_order<D: Dimension>(strides: &D) -> D
     let mut sorted = strides.clone();
     sorted.slice_mut().sort();
     let mut res = strides.clone();
-    for (ind, val) in strides.slice().iter().enumerate() {
-        // cannot binary search in unsorted...
+    for (ind, &val) in strides.slice().iter().enumerate() {
         let sorted_ind = sorted.slice()
-                               .binary_search(val)
-                               .expect("should be present");
+                               .iter()
+                               .enumerate()
+                               .find(|&(_, &x)| x == val)
+                               .unwrap().0; // cannot panic by construction
         res.slice_mut()[sorted_ind] = ind;
     }
     res