MAINT: cleaning up unused files
ENH: read_rsl can now read WSR-88D Level II data
BUG: distance and Barnes weighting in map_to_grid

* corrected distance calculation to use minkowski distance
* Barnes weighting function corrected
Updates to gridding functions for MMCG VAP
Merge pull request #54 from jjhelmus/master

Merging back in jjhelmus fork