chore: Alter whitespace for consistency

* Add newline after "I AM DONE" in exercises for consistency
* Remove trailing whitespace from exercises

exercises/conversions/as_ref_mut.rs

@@ -3,6 +3,7 @@
 // and https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
 
 // I AM NOT DONE
+
 // Obtain the number of bytes (not characters) in the given argument
 // Add the AsRef trait appropriately as a trait bound
 fn byte_counter<T>(arg: T) -> usize {

exercises/conversions/from_into.rs

@@ -18,7 +18,6 @@ impl Default for Person {
     }
 }
 
-// I AM NOT DONE
 // Your task is to complete this implementation
 // in order for the line `let p = Person::from("Mark,20")` to compile
 // Please note that you'll need to parse the age component into a `usize`
@@ -33,6 +32,9 @@ impl Default for Person {
 // 5. Extract the other element from the split operation and parse it into a `usize` as the age
 // If while parsing the age, something goes wrong, then return the default of Person
 // Otherwise, then return an instantiated Person object with the results
+
+// I AM NOT DONE
+
 impl From<&str> for Person {
     fn from(s: &str) -> Person {
     }

exercises/conversions/using_as.rs

@@ -1,9 +1,11 @@
 // Type casting in Rust is done via the usage of the `as` operator.
 // Please note that the `as` operator is not only used when type casting.
 // It also helps with renaming imports.
+//
+// The goal is to make sure that the division does not fail to compile
 
 // I AM NOT DONE
-// The goal is to make sure that the division does not fail to compile
+
 fn average(values: &[f64]) -> f64 {
     let total = values
         .iter()
@@ -14,4 +16,4 @@ fn average(values: &[f64]) -> f64 {
 fn main() {
     let values = [3.5, 0.3, 13.0, 11.7];
     println!("{}", average(&values));
-}
+}