Added vmin-vmax to contour and countourf
vmin-vmax don't work with contour

Made a recipe for contour plots. Apparently vmin-vmax aren't working for
contour. So I removed it from contour and left only in contourf.
Updated changelog for vmin-vmax args in contourf
Merge pull request #89 from leouieda/vmin-vmax-contourf

Added vmin and vmax to contourf