New Summary Statistics API for Java 8 streams

My goal is to design an updated summary statistics API for use with Java 8 streams based on the summary statistic implementations in the Commons Math stat.descriptive package. The project aims to be a library of commons statistics functions in line with the latest developments in the Java language, in particular Java's functional programming syntax. At the end of the project I plan to provide a lightweight and reusable API that utilizes Java streams to offer commonly used statistical functions, with an emphasis on minimizing external dependencies and avoiding redundancy.