[LIVY-440] Update copyright year to 2018

Author: Alex Bozarth <ajbozart@us.ibm.com>

Closes #79 from ajbozarth/440.

NOTICE

@@ -1,5 +1,5 @@
 Apache Livy
-Copyright 2017 The Apache Software Foundation
+Copyright 2018 The Apache Software Foundation
 
 This product includes software developed at
 The Apache Software Foundation (http://www.apache.org/).