fix some warnings

Author: melode11

src/internal/sio_client_impl.cpp

@@ -310,7 +310,7 @@ namespace sio
     unsigned client_impl::next_delay() const
     {
         //no jitter, fixed power root.
-        return min<unsigned>(m_reconn_delay * pow(1.5,m_reconn_made),m_reconn_delay_max);
+        return min<unsigned>(static_cast<unsigned>(m_reconn_delay * pow(1.5,m_reconn_made)),m_reconn_delay_max);
     }
 
     socket::ptr client_impl::get_socket_locked(std::string const& nsp)

src/internal/sio_packet.cpp

@@ -144,7 +144,7 @@ namespace sio
             if (mem_it!=value.MemberEnd() && mem_it->value.GetBool()) {
 
                 int num = value["num"].GetInt();
-                if(num >= 0 && num < buffers.size())
+                if(num >= 0 && num < static_cast<int>(buffers.size()))
                 {
                     return binary_message::create(buffers[num]);
                 }