Created primary API wrappers for the Isolator class

This is an attempt to abstract the internal workings of the isolator
class from the user application.

Change-Id: Ic898b202da6a0ddb368411c11218ca019d1f23fd
Signed-off-by: Zane Shelley <zshelle@us.ibm.com>
diff --git a/src/hei_includes.hpp b/src/hei_includes.hpp
index dbb8b35..36aa51a 100644
--- a/src/hei_includes.hpp
+++ b/src/hei_includes.hpp
@@ -10,5 +10,5 @@
 #include <hei_user_defines.hpp> // For HEI_ASSERT, HEI_INF, and HEI_ERR
 
 // Internal includes
-#include "hei_return_code.hpp"
+#include <hei_return_code.hpp>