Add reconstruct method to the regression model (#12)

Author: wildart

src/regressionmodel.jl

@@ -93,3 +93,19 @@ function predict! end
 Return the residual degrees of freedom of the model.
 """
 function dof_residual end
+
+"""
+    reconstruct(model::RegressionModel[, newY])
+
+Reconstruct explanatory variables from `model`.
+An object with new response values `newX` can be supplied, which should have
+the same type and structure as the output of [`predict(model)`](@ref).
+"""
+function reconstruct end
+
+"""
+    reconstruct!
+
+In-place version of [`reconstruct`](@ref).
+"""
+function reconstruct! end