GROMACS natively produces xvg output files for use with xmgrace. I don't like that too much, so this is a quick and incomplete way to plot those output files with matplotlib.
Download or clone the files, change to the gromacsplotter's top level directory and type
$ python setup.py install
You might need root access for that, or you can use the --user option to install only
for your account.
Since this is about quickly plotting the xvg output, a command line script is provided. After install, it should be in your PATH, so that you can use
$ gromacsplotter <name-of-xvg-file>
to create a plot. There are currently no options or arguments implemented. It will plot all the columns found in the file against the first column, and will try to read the axis labels and title from the xvg file.