get_dd_wind_field technique name potentially confusing for non-native English speakers

[rcjackson]

@ocepaf noted in his review of the PyDDA conference proceedings for SciPy that the current name of get_dd_wind_field could be confusing to non-native English speakers and suggested calculate or compute instead of get for the first word. I am open to suggestions here but am siding on using "compute."

This fits into PyDDA's roadmap of making it more accessible to non-English speakers, so it's a good addition to add.