Add NOTICE file (#1440)

This PR adds a NOTICE file repeating the copyright and license information of all third-party code.

Author: jtibshirani

NOTICE.md

@@ -0,0 +1,47 @@
+# NOTICE
+
+This project contains third-party material from the projects listed below.
+
+## ranger
+Ranger is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+Ranger is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with Ranger. If not, see <http://www.gnu.org/licenses/>.
+
+Written by:
+
+Marvin N. Wright
+Institut für Medizinische Biometrie und Statistik
+Universität zu Lübeck
+Ratzeburger Allee 160
+23562 Lübeck
+
+http://www.imbs-luebeck.de
+wright@imbs.uni-luebeck.de
+
+## Boost
+
+Copyright (c) 2014-2021 Martin Moene
+
+https://github.com/martinmoene/optional-lite
+
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+## Eigen
+
+This Source Code Form is subject to the terms of the Mozilla
+Public License v. 2.0. If a copy of the MPL was not distributed
+with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+## LLVM
+
+Licensed under the Apache License v2.0 with LLVM Exceptions: https://llvm.org/LICENSE.txt