Fix internal links (#143)

* Rename Readme to index to fix internal book links

Co-authored-by: simonsan <[email protected]>

Author: marcoieni

SUMMARY.md

@@ -2,7 +2,7 @@
 
 - [Introduction](./intro.md)
 
-- [Idioms](./idioms/README.md)
+- [Idioms](./idioms/index.md)
     - [Concatenating Strings with `format!`](./idioms/concat-format.md)
     - [Constructor](./idioms/ctor.md)
     - [The `Default` Trait](./idioms/default.md)
@@ -16,7 +16,7 @@
     - [Easy doc initialization](./idioms/rustdoc-init.md)
     - [Temporary mutability](./idioms/temporary-mutability.md)
 
-- [Design Patterns](./patterns/README.md)
+- [Design Patterns](./patterns/index.md)
     - [Builder](./patterns/builder.md)
     - [Compose Structs](./patterns/compose-structs.md)
     - [Fold](./patterns/fold.md)
@@ -26,10 +26,10 @@
     - [Contain unsafety in small modules](./patterns/unsafe-mods.md)
     - [Visitor](./patterns/visitor.md)
 
-- [Anti-patterns](./anti_patterns/README.md)
+- [Anti-patterns](./anti_patterns/index.md)
     - [`#[deny(warnings)]`](./anti_patterns/deny-warnings.md)
     - [Deref Polymorphism](./anti_patterns/deref.md)
 
-- [Functional Programming](./functional/README.md)
+- [Functional Programming](./functional/index.md)
 
 - [Additional Resources](./additional_resources.md)

anti_patterns/README.md renamed to anti_patterns/index.md

@@ -7,13 +7,13 @@ When developing programs, we have to solve many problems. A program can be viewe
 
 There are many problems that share the same form. Due to the fact that Rust is not object-oriented design patterns vary with respect to other object-oriented programming languages. While the details are different, since they have the same form they can be solved using the same fundamental methods. 
 
-[Design patterns](https://rust-unofficial.github.io/patterns/patterns/index.html) are methods to solve common problems when writing software.
+[Design patterns](./patterns/index.md) are methods to solve common problems when writing software.
 
-[Anti-patterns](https://rust-unofficial.github.io/patterns/anti_patterns/index.html) are methods to solve these same common problems. 
+[Anti-patterns](./anti_patterns/index.md) are methods to solve these same common problems. 
 
 However, while design patterns give us benefits, anti-patterns create more problems.
 
-[Idioms](https://rust-unofficial.github.io/patterns/idioms/index.html) are guidelines to follow when coding. They are social norms of the community. 
+[Idioms](./idioms/index.md) are guidelines to follow when coding. They are social norms of the community. 
 You can break them, but if you do you should have a good reason for it. 
 
 TODO: Mention why Rust is a bit special - functional elements, type system, borrow checker

functional/README.md renamed to functional/index.md

@@ -0,0 +1,15 @@
+# Refactoring
+
+Refactoring is very important in relation to these topics. Just as important as the other topics covered here, is how to take good code and turn it into great code.
+
+We can use [design patterns](patterns/index.md) to DRY up code and generalize abstractions. We must avoid [anti-patterns](anti_patterns/index.md) while we do this. While they may be tempting to employ, their costs outweigh their benefits.
+
+> Shortcuts make for long days.
+
+We can also use [idioms](idioms/index.md) to structure our code in a way that is understandable. 
+
+## Tests
+
+Tests are of vital importance during refactoring.
+
+## Small changes