bilinear interpolation fails if src lat != 0

[nbren12]

For example, if lat = [0.5, 1.5, ...], then the bilinear interpolation does not correctly wrap around.

[nbren12]

Solution:

            lon_center = self.ds.lon.values
            # need to workaround bug where earth2grid fails to interpolate in circular manner
            # if lon[0] > 0
            # hack: rotate both src and target grids by the same amount so that src_lon[0] == 0
            # See https://github.com/NVlabs/earth2grid/issues/21
            src_lon = lon_center  - lon_center[0]
            target_lon = (target_grid.lon - lon_center[0]) % 360