README: update copyright to 2018

Author: randallwhitman

README.md

@@ -53,7 +53,7 @@ Find a bug or want to request a new feature?  Please let us know by submitting a
 Esri welcomes contributions from anyone and everyone. Please see our [guidelines for contributing](https://github.com/esri/contributing)
 
 ## Licensing
-Copyright 2013-2017 Esri
+Copyright 2013-2018 Esri
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.