several changes made in exercises 12 and 13. Exercise 12: changed the div image to be able to place an image; major changes: box-border for img and p, display block for img, no need for height, margin 0 auto to center image, gave width 30% to image div and 70% for p; Exercises 13: made changes and cleaned up; noticed interesting case for using overflow: auto together with height - interesting because there is a vertical scrolling bar appearing if height is too low; I changed this by removing height first, and then later added height: auto together with overflow
Merge branch 'master' into gh-pages