Install headers prefixed, as to not cause a possible conflict with
different versions.

--- templates/lib/CMakeLists.txt.orig	2016-08-10 16:06:08 UTC
+++ templates/lib/CMakeLists.txt
@@ -119,7 +119,7 @@ install(TARGETS grantlee_core EXPORT gra
          RUNTIME DESTINATION ${BIN_INSTALL_DIR} COMPONENT Templates
          LIBRARY DESTINATION ${LIB_INSTALL_DIR} COMPONENT Templates
          ARCHIVE DESTINATION ${LIB_INSTALL_DIR} COMPONENT Templates
-         INCLUDES DESTINATION include
+         INCLUDES DESTINATION include/grantlee4
 )

 install(FILES