Document Tridiagonalization class, remove unused types.
diff --git a/doc/snippets/Tridiagonalization_decomposeInPlace.cpp b/doc/snippets/Tridiagonalization_decomposeInPlace.cpp
new file mode 100644
index 0000000..2e53af7
--- /dev/null
+++ b/doc/snippets/Tridiagonalization_decomposeInPlace.cpp
@@ -0,0 +1,10 @@
+MatrixXd X = MatrixXd::Random(5,5);
+MatrixXd A = X + X.transpose();
+cout << "Here is a random symmetric 5x5 matrix:" << endl << A << endl << endl;
+
+VectorXd diag(5);
+VectorXd subdiag(4);
+Tridiagonalization<MatrixXd>::decomposeInPlace(A, diag, subdiag);
+cout << "The orthogonal matrix Q is:" << endl << A << endl;
+cout << "The diagonal of the tridiagonal matrix T is:" << endl << diag << endl;
+cout << "The subdiagonal of the tridiagonal matrix T is:" << endl << subdiag << endl;