Functions rxLinPredError.R

Function calculates the MSE, MAPE, MPE, and MSWD
Merge pull request #1 from ChibisiAtRevolution/master

Functions rxLinPredError.R
Added rxAIC()
Added rxLinPredError()
Improved documentation
Added NEWS file; Bumped version to 0.0-03
Merge pull request #8 from andrie/master

Added rxLinPredError(), rxAIC() and NEWS file