Use shared pointer when binding callback for serial read (#38)

* Resolves an issue with ROS Melodic on 18.04.

src/serial.cpp

@@ -72,7 +72,7 @@ namespace create {
     // Start continuously reading one byte at a time
     boost::asio::async_read(port,
                             boost::asio::buffer(&byteRead, 1),
-                            boost::bind(&Serial::onData, this, _1, _2));
+                            boost::bind(&Serial::onData, shared_from_this(), _1, _2));
 
     ioThread = boost::thread(boost::bind(&boost::asio::io_service::run, &io));
 
@@ -145,7 +145,7 @@ namespace create {
     // Read the next byte
     boost::asio::async_read(port,
                             boost::asio::buffer(&byteRead, 1),
-                            boost::bind(&Serial::onData, this, _1, _2));
+                            boost::bind(&Serial::onData, shared_from_this(), _1, _2));
   }
 
   bool Serial::send(const uint8_t* bytes, unsigned int numBytes) {