Update README

Add problem statement, example usage for a generic correlation coefficient, and dependencies
Setup

Modified README to include mean and standard deviation. Added the concepts header that is
required to use with the experimental compiler. Added empty fraud file to hold template
functions, test suite setup, and CMake support
Concrete and generic implementation of correlation coefficient.

Tested with double arrays, then added concept for iterators to generically implement sum, mean, variance,
standard deviation, and correlation coefficient. Add test cases.
Update README