area 0.2.0

Improved C++ sum method to match benchmarks (from 2023 advent of code Day 18, see #4). Thanks to Tan Ho, Jonathan Carroll, and Rich FitzJohn.

area 0.1.0

Now use cpp11.
Added C++ versions of triangle and polygon area.
Begin conversion to C++ headers capability.

area 0.0.1

First working version using R code only.