note python 3 compat in readme
make sure test files read are utf-8
reimplement grid.resample

new grid.resample (only nearest neighbour) is faster, fewer lines of code, and
passes tests

grid.resample no longer tries to use scipy
temporary grid.resample_griddata

a wrapper for griddata interpolation
refactor md5sum function

split file logic out into md5sum_file -- it's good to know exactly what a
function is going to do
disable test_mp2vtp

in Python 3, the output of ElementTree.tostring isn't deterministic, so the
generated VTK doesn't always match the reference data. This is a testing bug.