Changes and Corrections to Project #1 from Original Handout

The following changes have been incorporated into the online versions of
the project.

1. Add the / operator.  For example   
	5 4 /
   leaves 1.25 on the stack.  It is defined only for numbers.

2. There are numerous corrections to the examples. They should now read as
   follows:

	% java mcalc
	Mcalc, version 1.0 
	> # Here are some examples 
	> 3 4 / 4 5 / * 8 + 4 / = 
	2.15 
	> [1 2 -1] 
	> [2 3 
	>  3] t * =
	5 
	> [[1 2 3] [4 5 6]] =: A 
	> [1 2 1] =: x 
	> := A := x t * = 
	[8 20]t 
	> q

3. Variables (as used with := and =:) consist only of letters, digits, and
   underscores (like Java identifiers, rather than being arbitrary strings 
   of non-whitespace).  This is to make input a bit easier 
   with StreamTokenizer.

4. We will treat [ x ] as if it were x, for any single item x (number,
   row, column).  Row vectors are just 1xn matrices, and column vectors
   are mx1 matrices.  Strictly speaking, this is not formally correct,
   but practically, it works just fine.

5. Because it is now functioning as Matrix, Vector, and scalar, I have
   changed the name of the single class in mymath to Quantity, rather than
   have Matrix and Vector classes.