rework Identity API: no longer restricted to square matrices
diff --git a/doc/snippets/MatrixBase_identity.cpp b/doc/snippets/MatrixBase_identity.cpp
new file mode 100644
index 0000000..cac2a72
--- /dev/null
+++ b/doc/snippets/MatrixBase_identity.cpp
@@ -0,0 +1 @@
+cout << Matrix<double, 3, 4>::identity() << endl;
diff --git a/doc/snippets/MatrixBase_identity_int.cpp b/doc/snippets/MatrixBase_identity_int.cpp
deleted file mode 100644
index 8cf39d9..0000000
--- a/doc/snippets/MatrixBase_identity_int.cpp
+++ /dev/null
@@ -1,2 +0,0 @@
-cout << Matrix2d::identity() << endl;
-cout << MatrixXd::identity(3) << endl;
diff --git a/doc/snippets/MatrixBase_identity_int_int.cpp b/doc/snippets/MatrixBase_identity_int_int.cpp
new file mode 100644
index 0000000..5b2adfc
--- /dev/null
+++ b/doc/snippets/MatrixBase_identity_int_int.cpp
@@ -0,0 +1 @@
+cout << MatrixXd::identity(4, 3) << endl;