Ruby port: LtRt Matrix Decoder JSFX plugin

This is a Ruby port of T.J. Vincent's LtRtMatrixDecoder JSFX plugin (https://github.com/MPdecode/LtRtMatrixDecoder).

In combination with Joel Strait's wavefile gem (https://github.com/jstrait/wavefile) we can access and convert LtRt files to LRCS/4.0 or LRC/3.0 files in native Ruby.