feat!: Scale improvements

- Added dedup of scale points
- Changed visibility of some Scale functions
- Added length of scale
- Corrected line scales test
- Changed Scale::contains to consider entire generated range
- Changed Scale::new to accept friendlier inputs
- Changed Scale::points to return uniform Data type
- Added Scale tests

Author: EmmanuelDodoo

src/models/bar.rs

@@ -123,13 +123,11 @@ mod barchart_tests {
 
         let x_scale = {
             let rng = 0..60;
-            let rng = rng.into_iter().map(From::from);
 
             Scale::new(rng, ScaleKind::Integer)
         };
         let y_scale = {
             let values = vec!["one", "two", "three", "four", "five"];
-            let values = values.into_iter().map(ToOwned::to_owned).map(From::from);
 
             Scale::new(values, ScaleKind::Text)
         };
@@ -152,13 +150,11 @@ mod barchart_tests {
 
         let x_scale = {
             let rng = -5..11;
-            let rng = rng.into_iter().map(From::from);
 
             Scale::new(rng, ScaleKind::Integer)
         };
         let y_scale = {
             let rng = 2..10;
-            let rng = rng.into_iter().map(From::from);
 
             Scale::new(rng, ScaleKind::Integer)
         };