added tests for io and memory plot creation.

found out a couple of interesting things. If you want nice mouse rotatable 3d graphs you
want to use terminal x11. The html5 canvas terminal does not work. Also, using a multiplot
 prevents you from interacting with your nice 3d graphs with the x11 terminal. Only single
 plots are rotatable which is a real shame.

 svg terminalm is preferable over png. Also created svg images can have javascript embedded
 within them to allow very minor mouse interaction (disabling certain lines). svg is now the output.