remove calls to axes.set_xticklabels -- not robust.
axis labels come out wrong if zooming or adding additional plots
rotate ticklabels in dtopotools
fix test problem so works if run manually
improved rotation in dtopotools.py
improved rotation in topotools.py
remove un-needed plt.sca
Merge pull request #114 from rjleveque/dtopotools2

remove calls to axes.set_xticklabels -- not robust.