std.unittests for (final?) review

[Tomek Sowiński]

Andrei Alexandrescu napisał:

> * Remove assertCmp and fold it into assertPredicate. With trivial 
> metaprogramming you can distinguish an operator from an actual expression.
> 
> assertPredicate!"<"(1 + 1, 2.1);

If it's trivial, put it into binaryFun, so that everyone else can reap rewards:

sort!">"(range);
auto sum = reduce!"+"(range);

As for operator-only unaryFuns, don't; they bring more confusion than benefit.

-- 
Tomek