Savitzky-Golay filter implementation

DEPRECATED The code of this project has been extracted from https://raw.githubusercontent.com/thatchristoph/vmd-cvs-github/master/plugins/signalproc/src/sgsmooth.C, and simply packaged in an easy to compile and install way with cmake. I am not the original author of the library.

Since then, I have found the need to implement my own version of Savitzky Golay filters based on Gram polynomials. I recommend looking at my own implementation which is easier to use and more complete than the one in this repository: https://github.com/arntanguy/gram_savitzky_golay