REQUIRE_THROWS_AS now catches exception by const&

Prevents some warnings caused by catching complex types by value.

Closes #542
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6fe4e4e..e9a00c2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -195,6 +195,7 @@
         ${HEADER_DIR}/internal/catch_tostring.h
         ${HEADER_DIR}/internal/catch_tostring.hpp
         ${HEADER_DIR}/internal/catch_totals.hpp
+        ${HEADER_DIR}/internal/catch_type_traits.hpp
         ${HEADER_DIR}/internal/catch_version.h
         ${HEADER_DIR}/internal/catch_version.hpp
         ${HEADER_DIR}/internal/catch_wildcard_pattern.hpp