gridder.interp uses scipy.interpolate.griddata and extrapolates data
Added option for nearest neighbors using matplotlib to gridder.interp
Recipe for gridder interpolation uses different methods
Separated gridder.interp in 2 function: 1 interpolated at given points,
other interpolates on regular grid. Added function to extrapolated
masked arrays or NaNs
Updated changelog
Recipe of using gridder.interp_at to extract a profile from grid data
Forgot to mock scipy.interpolate in docs
Merge pull request #44 from leouieda/extrapolation

Better interpolators and extrapolation for `gridder`