Add Client class, which wraps socket functionality

Wrap the functionality of creating and connecting to a server and writing and
reading data. Create a class called Client to do this. There is no change in
functionality - it still writes the first header, reads the response, and exits.
Set error for sucess at beginning of functions.
Correct comment for hints socket type
Edit include guard in socket.hpp to match file name
Use class member initializer instead of initializer list

Yay C++11
Add sammbox namespace around Client class
Merge pull request #8 from tcoyne/socket

Add Client class, which wraps socket functionality