scope hei_bit_string.hpp for external use

This header will been needed by user applications.

Signed-off-by: Zane Shelley <zshelle@us.ibm.com>
Change-Id: I4eae57c63e3d314d87faed364a3c314c2300d20a
diff --git a/test/bit_string_test.cpp b/test/bit_string_test.cpp
index 923d503..d329beb 100644
--- a/test/bit_string_test.cpp
+++ b/test/bit_string_test.cpp
@@ -1,4 +1,4 @@
-#include <util/hei_bit_string.hpp>
+#include <hei_bit_string.hpp>
 
 #include "gtest/gtest.h"