NEW FEATURE: Animation support #11

Summary

Animation when time axis present.

Reason

To compete with ncview, it would be nice to show the time-evolution of a netcdf variable within a mapplot.

Detailed explanation

Matplotlib provides animations, so it shouldn't be to hard to make a simple interface like ncview provides, with next/previous frame, play forward/backward and delay.

Example

Thanks for the great package!
Cheers, Sebastian