Fixes

- Removed void* arithmetic
- Fixed connection_send does not return anything
- Fixed server_events invalid args in main.c (and changed its
  declaration)

connection.h

@@ -40,6 +40,8 @@ bool connection_is_socket_managed(int fd);
 //  - true on success
 //  - false on failure
 // Remarks:
+//  - you must make sure fd is managed by this module
+//    (use connection_is_socket_managed)
 //  - the app should be terminated if this function returns false
 void connection_event(int fd, uint32_t events);