Please include support for boost 1.70

[mcelhennyi]

Issue

In boost 1.7 the use of the io_context and the strand has been changed. This causes a breaking change in the Socket/Connection.cpp compilation in the constructor for the variable m_strand and m_heartbeatTimer. The call to p_socket.get_executor().context() fails and is no longer supported.

Below are some links to similar posts about this in other places:
boost asio issues
rstudio issues
boost docs
boost beast issues

Changes to get it building

• I cloned the repo, removed the m_strand from the Connection.h/cpp file.
• I replaced line 62 boost::asio::ip::tcp::socket socket(m_ioContext); in client.cpp with boost::asio::ip::tcp::socket socket(boost::asio::make_strand( m_ioContext ));
• I changed the m_heatbeatTimer construction in the connection.cpp file to be this instead m_heartbeatTimer(p_socket.get_executor())

I am unsure if these changes are proper, but it was enough to get it building and for my use I will not need this class. I see there are other topics about this, but this seems like a simple fix if what I did is still semantically/functionally correct (my knowledge of boost is very low).