Headers and typos

Author: sebmarkbage

README.md

@@ -31,7 +31,7 @@ let gen = (function*() {
 })();
 ```
 
-This can be combined with various initializers to create an Array, Maps or Set.
+This can be combined with various initializers to create an Arrays, Maps or Sets.
 
 ```js
 let arrayOfUsers = [...*{
@@ -66,6 +66,8 @@ let mapOfUsers = new Map(*{
 });
 ```
 
+## Code Evolution
+
 Since these generator expressions naturally expand to more complex examples, you can keep expanding these with more complex logic as requirements expand. While still remaining in an isolated expression.
 
 ```js