Introduction/Design Patterns Revisited - Markdown

Hi Bob,

This pull request includes my edits to the following *Game Programming Patterns* chapters:

**Introduction**
* Architecture, Performance, and Games

**Design Patterns Revisited**
* Command
* Flyweight
* Observer
* Prototype
* Singleton
* State

This request only includes edits to the Markdown files. Unfortunately, I was unable to get the updated script running (probably due to user error :)). When I entered "python script/format.py --watch" from the "game-programming-patterns" folder, nothing happened. Is there anything else besides Python Markdown, Pygments, and Smartypants that I might need?

Please note that I encountered a few of the outstanding style guide questions while editing, and this is how I handled each item:

* I formatted "enum" and "switch" as code. It seemed better for clarity, and they are formatted as code in seemingly professional publications (for example, http://msdn.microsoft.com/en-us/library/06tc147t.aspx). 
* I used parentheses when referring to methods and functions because you seemed to do that more often than not in the text. Plus, I think it's helpful for the reader (or at least for me) to remember that what you are referring to is a method or function and not something else.
* I continued to NOT use ":" before illustrations. I think it makes sense to use ":" when introducing code since you usually write something such as, "...something like this:", directly referring to the following code block. This is not always the case for illustrations, so ending sentences preceding illustrations with a period makes sense.

Please let me know if you have any questions.

Thanks!