Add ability to connect using UNIX socket

Add ability to connect to a Redis server using UNIX socket by
specifying the unix_socket_path parameter
Fix simple demo

Add missing connect instruction to make simple demo work.
Maybe the creation of the client should be moved outside of the
functions like in the websocket example.
Revert "Fix simple demo"

This reverts commit 9c0e3ca33b8ca903a63333c4065e51a579631541.
Merge pull request #30 from studer/master

Add ability to connect using UNIX socket