Minor editorial revisions to intro

[sh0ji]

These are my edits per #519.

[mcking65]

Thank you @sh0ji. Looks good except for one small issue on line 71 that I will fix after merging.

For future PRs, I can make a cleaner history if you make your changes in a branch in your fork and then leave the box checked that allows me to push to that branch. Then, I would have been able to make the minor correction, push it to your fork, and then squash the 2 commits when I merge into the practices repo.