extendmatrix 0.2.3

The project consists of some enhancements to the Ruby "Matrix" module and includes: LU and QR (Householder, Givens, Gram Schmidt, Hessenberg) decompositions, bidiagonalization, eigenvalue and eigenvector calculations. Include some aditional code to obtains marginal for rows and columns. Original code from http://rubyforge.org/projects/matrix/ , done by Cosmin Bonchis as a Google Summer of Code 2007 project for Ruby Central Inc. Gem, github repository and current version manteined by Claudio Bustos.