Dictionary implementation updated

[Brian T Rice]

I spent enough time to complete the SaferDictionary implementation, which
unlike Smalltalk implementations, does not use Association objects, but
instead uses two separate arrays for the keys and values. This winds up
being clearer in the implementation as well as using less memory (unless
you call associationsDo: a lot, which is not a common Smalltalk idiom:
keysAndValuesDo: is equivalent and just as useful).

I performed some basic tests, and then merged and retested the code, so
all should be well. Let me know if you have any problems with it.

-- 
Brian T. Rice
LOGOS Research and Development
http://tunes.org/~water/