TODO: test case for plotting

plot title and labels.
plot from a vertical transect
multiprocess transects
Force Agg backend for plotting

Not sure why we have to force the Agg backend when we are using ssh -x
and DISPLAY is set.

This is the error:

> The program 'python' received an X Window System error.
> This probably reflects a bug in the program.
> The error was 'BadIDChoice (invalid resource ID chosen for this connection)'.
>   (Details: serial 557 error_code 14 request_code 53 minor_code 0)
>   (Note to programmers: normally, X errors are reported asynchronously;
>    that is, you will receive the error a while after causing it.
>    To debug your program, run it with the --sync command line
>    option to change this behavior. You can then get a meaningful
>    backtrace from your debugger if you break on the gdk_x_error() function.)
make test imports relative
contour plot at 50