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
adding an mwb version of Diagram 4.11
adding diagram 4.11 in dia format, which appears to be what the author used
removing mwb format.  It would be too confusing at this point.
updating to let folks know not to use MySQL Workbench for E/R diagrams