message: Fix license in contributing guidelines
diff: @@ -60,7 +60,7 @@ General structure:
  Example:
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
  -// Copyright 2014 MongoDB Inc.
  +// Copyright 2018-present MongoDB Inc.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  