Update application after working through the first five exercises at the end of chapter 9. I am about to start
working on example #6 at the end of chapter 9, which may require a decent amount of new code, so I figure that
this is a good time to log a commit.
Add the code that was necessary to complete most of the exercises at the end of chapter 9. I was not able to
do much with problem 7 and did not even attempt problem 9, but at least the app is synced up and is functioning
properly. Note that omitting the code for problem 9 means that there is a chance that an Admin user would be able
to delete himself by making an explicit request to the users#delete action and passing in the parameters for their
own profile, but it is highly unlikely that this would actually happen in practice. These exercises may get revisited
at some point in the future, but for now the app is ready to start in at the beginning of chapter 10.