Fixing lots of warnings. Removed NotImplementedException references.
Removed dead code.
Undo changes to .classpath file
(1) Model data is now pulled by LetterPageView instead of being pushed
to it.  This eliminates the LetterPageView's dependency on Letter.  (2)
Re-added methods to LetterPageController to support change #1.  (3)
Updated JUnits tests to eliminate failures.  (4) Cleaned up more
warnings.  (5) Deleted some duplicated code in JUnit tests.
Removed more duplicated test code.
(1) Updated test code and added several checks for null in application
code so that all JUnit tests pass without any failures or errors.
Additional minor cleanup of test classes.
Modified application to target Java 6 (1.6) since not everyone in the
group can run with Java 7 yet.  Similarly, removed <String> from
JComboBox declarations.
Merge pull request #59 from CS673/clean-up-warnings-1a

Clean up warnings & removal of duplicated test code.