correct markup typo

I just started reading the book and after struggling with the fact that the code examples in the book weren't executable as is I thought I'd see if anyone had started a project to assemble a repository of working code. Lo and behold, I came across your reddit post mentioning that you had put together this repository. Great work!

I found this minor markup error that resulted in some normal text being formatted as code
![pearls_chap01_at_master__seako_pearls](https://cloud.githubusercontent.com/assets/380159/2688403/650931ae-c29b-11e3-8eda-49c3a1d22e0f.jpg)

Here's what it looks like after the change
![_corrected__pearls_chap01_at_master__seako_pearls](https://cloud.githubusercontent.com/assets/380159/2688414/003da5ba-c29c-11e3-9d90-db26ce81f89f.jpg)