Update README.md

README.md

@@ -37,15 +37,15 @@ catered for.
 
 ## Contents
 
-1. [Introduction - Hello world!](hello%20world.md)
-1. [Control flow](control%20flow.md)
+1. [Introduction - Hello world!](hello-world.md)
+1. [Control flow](control-flow.md)
 1. [Primitive types and operators](primitives.md)
 1. [Unique pointers](unique.md)
 1. [Borrowed pointers](borrowed.md)
-1. [Rc and raw pointers](rc%20raw.md)
-1. [Data types](data%20types.md)
+1. [Rc and raw pointers](rc-raw.md)
+1. [Data types](data-types.md)
 1. [Destructuring pt 1](destructuring.md)
-1. [Destructuring pt 2](destructuring%202.md)
+1. [Destructuring pt 2](destructuring-2.md)
 1. [Arrays and vecs](arrays.md)
 1. [Graphs and arena allocation](graphs/README.md)
 1. [Closures and first-class functions](closures.md)