added week 5 homework.
-Sheeri
added week 6 homework
adding question 6 to chapter 5 homework
updating the badges URL
fixing ansi vs. theta
adding homework for week 7
fixing typo
updating homework
fixing queries in q6
adding homework for chapters 8 and 9
adding chapter 10 homework
adding optional exercises to chapter 10
adding homework for chapters 11 and 12
fixing typo
adding a bit more to the questions
fixing typo
updating to let folks know not to use MySQL Workbench for E/R diagrams
update