[Checkers] Notice about Added Feature

[Mahmood Ali]

Hi Mike,

For the nullness demo, I decided to change my nullness example to  
JUnit 4.4, where Assert.equals(actual, expected) throws an NPE, when  
actual is null but expected is not.  The example is straight forward  
and effective (I think), as junit is commonly used library.

Also, for the purpose of the demo, I would like to add a check for  
redundant nullness checking.  Given an nullness test (via equality),  
the nullness checker would report a *warning* if a nonnull value is  
tested for nullness.  Unfortunately, we cannot add a warning for known- 
to-be null tested against a NonNull reference. (i.e. String s = null;  
if (s == "m") { .... }).  The check is disabled by default, and  
activated via (-Alint=+redundant).

- Mahmood