Add a license to vtkm.

LICENSE.txt

+VTKm License Version 1.0
+========================================================================
+
+Copyright (c) 2014,
+Sandia Corporation, Los Alamos National Security, LLC.,
+UT-Battelle, LLC., Kitware Inc., University of California Davis
+All rights reserved.
+
+Sandia National Laboratories, New Mexico
+PO Box 5800
+Albuquerque, NM 87185
+USA
+
+UT-Battelle
+1 Bethel Valley Rd
+Oak Ridge, TN 37830
+
+Los Alamos National Security, LLC
+105 Central Park Square
+Los Alamos, NM 87544
+
+Kitware Inc.
+28 Corporate Drive
+Clifton Park, NY 12065
+USA
+
+University of California, Davis
+One Shields Avenue
+Davis, CA 95616
+USA
+
+Under the terms of Contract DE-AC04-94AL85000, there is a
+non-exclusive license for use of this work by or on behalf of the
+U.S. Government.
+
+Under the terms of Contract DE-AC52-06NA25396 with Los Alamos National
+Laboratory (LANL), the U.S. Government retains certain rights in
+this software.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+ * Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+
+ * Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the
+   distribution.
+
+ * Neither the name of Kitware nor the names of any contributors may
+   be used to endorse or promote products derived from this software
+   without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR
+CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+========================================================================
+
+The following files and directories come from third parties. Check the
+contents of these for details on the specifics of their respective
+licenses.
+- - - - - - - - - - - - - - - - - - - - - - - - do not remove this line
+CMake/CheckCXX11Features.cmake
+CMake/FindBoostHeaders.cmake
+vtkm/testing/OptionParser.h