rename socket.cpp/h to CC3000_socket.cpp/h

See [here](https://forums.adafruit.com/viewtopic.php?f=31&t=60840) for context.

Socket.cpp/h need to be renamed to CC3000_socket.cpp/h to avoid conflict with the Ethernet library.  This is a very safe change that I believe will help people avoid this problem in the future.

I also removed the unnecessary folder specifier from sntp.h