Add code blocks to the ch17 (practicing-bdd)

[bocharsky-bw]

Resolve 17-practicing-bdd in #12

[weaverryan]

@bocharsky-bw sometimes, there's 1 line between 2 lines that we want to show. I think if that line is blank (or has something else not important, like a comment), we should show it. That way, I can see that it is just a blank line - if I see the ... in the code block (which takes up the same amount of space), it's less clear what details we're hiding :). For example, line 34 is just a blank line:

[weaverryan]

And on that same code-block, I added the if statement context around it. This gives it more context "where does this go?" - but as a negative, the code block is now a mix of new stuff and old stuff. Here's what I changed the block to:

What is your opinion of doing this?

[bocharsky-bw]

@weaverryan Hm, it's really difficult question. I have not thought well about this before... I think more context is worth mix of new / old stuff here.