Initially works with T_ady_2d, the advective component. The full
heat transport should also inclide T_diffy_2d. If the script is
invoked with only T_ady_2d, a warning message is printed to the
screen and annoateed to the plot.

Feature enhancements:
  - Ability to read either gridspec directory or tar file
  - On-line basin mask generation if basin mask file is
    missing

Added a Makefile to run tests of the common frepp analysis
scripts on both the 0.25 and 0.5 degree configurations.

 - Added heat transport diagnostic to OM4_025 example
 - Added .frepp files for OM4_05 example