Drive home point of DIP and decoupling

Author: ryanmcdermott

README.md

@@ -1084,11 +1084,15 @@ This can be hard to understand at first, but if you've worked with Angular.js,
 you've seen an implementation of this principle in the form of Dependency
 Injection (DI). While they are not identical concepts, DIP keeps high-level
 modules from knowing the details of its low-level modules and setting them up.
-It can accomplish this through DI.
+It can accomplish this through DI. A huge benefit of this is that it reduces
+the coupling between modules. Coupling is a very bad development pattern because
+it makes your code hard to refactor.
 
 As stated previously, JavaScript doesn't have interfaces so the abstractions
 that are depended upon are implicit contracts. That is to say, the methods
-and properties that an object/class exposes to another object/class.
+and properties that an object/class exposes to another object/class. In the
+example below, the implicit contract is that any Request module for an
+`InventoryTracker` will have a `requestItems` method.
 
 **Bad:**
 ```javascript