fix some typos (#30)

Author: vol1ura

README.md

@@ -13,7 +13,7 @@ Summary of the design patterns explained in the book [Design Patterns in Ruby](h
 * [Decorator](decorator.md): vary the responsibilities of an object adding some features
 * [Factory](factory.md): create objects without having to specify the exact class of the object that will be created
 * [Interpreter](interpreter.md): provides a specialized language to solve a well defined problem of know domain
-* [Iterator](iterator.md): provides a way to access a collection of sub-objects without exposing the underlaying representation
+* [Iterator](iterator.md): provides a way to access a collection of sub-objects without exposing the underlying representation
 * [Observer](observer.md): helps building a highly integrated system, maintainable and avoids coupling between classes
 * [Proxy](proxy.md): allows us having more control over how and when we access to a certain object
 * [Singleton](singleton.md): have a single instance of certain class across the application

adapter.md

@@ -51,7 +51,7 @@ class StringIOAdapter
 end
 ```
 
-Now we can use a `String` as if it were an open file (it only implements a small part of the `IO` interface, essentally what we need).
+Now we can use a `String` as if it were an open file (it only implements a small part of the `IO` interface, essentially what we need).
 
 ```ruby
 encrypter = Encrypter.new('XYZZY')

iterator.md

@@ -1,7 +1,7 @@
 # Iterator Pattern
 
 ## Problem
-We have an aggregate object and we want to provide a way to access its collection of sub-objects without exposing its underlaying representation.
+We have an aggregate object and we want to provide a way to access its collection of sub-objects without exposing its underlying representation.
 
 ## Solution
 There are two proposed solutions: **external iterators** and **internal iterators**.

strategy.md

@@ -54,7 +54,7 @@ class PlainTextFormatter
 end
 ```
 
-To use it, we just provide a formated object (strategy) to the report (context)
+To use it, we just provide a formatted object (strategy) to the report (context)
 
 ```ruby
 report = Report.new(HTMLFormatter.new)