Fixes an issue with libc++ eof handling in rapidjson

The credit to this fix is due to @zittix. This closes issue strands-project#51.

This is due to a bug in the mac version of libc++ and should be fixed in
HEAD. See here for a related stackoverflow post:
http://stackoverflow.com/questions/14147667/clang-and-libc-istreampeek-does-not-set-eof-flag

include/cereal/external/rapidjson/reader.h

@@ -250,7 +250,7 @@ class GenericReader {
 			}
 			SkipWhitespace(stream);
 
-			if (stream.Peek() != '\0')
+			if (stream.Peek() != '\0' && stream.Peek() != static_cast<Ch>(std::char_traits<Ch>::eof()))
 				RAPIDJSON_PARSE_ERROR("Nothing should follow the root object or array.", stream.Tell());
 		}