fix build on travis-ci

zhijunfu · zhijunfu · commit b5b2fac29f5b · 2018-05-04T12:00:48.000+08:00
diff --git a/cpp/src/plasma/io.h b/cpp/src/plasma/io.h
@@ -25,6 +25,7 @@
 
 #include <string>
 #include <vector>
+#include <memory>
 
 #include "arrow/status.h"
 #include "plasma/compat.h"
