Constant<T>.Pi requires GreaterThanOrEqual to be defined

[WhiteBlackGoose]

To be precise, in this line

pi = Maximum(pi, Constant<T>.Three);

It's better to first check whether the class has this operator defined, it's obviously unnecessary for this line, but it's called when Constant.One is called.

My solution is presented in #56, but I don't think it fits the code quality requirements

[ZacharyPatten]

There is still more that will need to be done to the ComputePi method... But I went ahead and converted it to a property along with all the members of Constant. Using fields was faster than properties, but I've determined there are better ways to handle optimizations than worrying about the members of Constant being fields.

[WhiteBlackGoose]

It's a matter of a few nanoseconds, I don't think it's a big issue for those who use c#.