Rename integers.hpp to types.hpp in case floating point is someday supported.

test/speed_test.cpp

@@ -12,7 +12,7 @@
 #include <boost/endian/detail/disable_warnings.hpp>
 
 #include <boost/endian/conversion.hpp>
-#include <boost/endian/integers.hpp>
+#include <boost/endian/types.hpp>
 #include <boost/cstdint.hpp>
 #include <boost/timer/timer.hpp>
 #include <iostream>