Improvement to std.numeric examples in documentation

[BoraxMan]

For the normalize function in std.numeric, I think an example of 
how to use bool normalize(R) where there is a sum value provided 
should be included.

The reason for this is that the examples given are as follows, 
and none show how the second sum parameter is given.

double[] a = [];
assert(!normalize(a));
a = [ 1.0, 3.0 ];
assert(normalize(a));
writeln(a); // [0.25, 0.75]
a = [ 0.0, 0.0 ];
assert(!normalize(a));
writeln(a); // [0.5, 0.5]

When one tries to do something like "normalize(a,10)", dmd 
reports this error.

> Error: template instance normalize!(no, 100) does not match 
> template declaration normalize(R)(R range, ElementType!R sum = 
> 1)

One must actually specify the template parameter, thus

> assert(normalise!(typeof(a)(a,100));

I guess for those more familiar with the language, this would be 
clear, but for those not as familiar just wanting to use a 
standard library function, they may be wondering why simply 
adding the second 'sum' parameter causes an error, or why IFTI 
isn't working.  I know I got a little stuck.




I also wonder why this second parameter means that DMD cannot 
deduce the type that (R) is.