Applied python-modernize to pyresample.
Got rid of dependencies on the six package.
Multiple small fixes to make the code work on both Python 2 and 3. shmem_as_ndarray() now uses numpy.frombuffer() to provide equivalent functionality.
Made testing of a Proj4 string independent of the order of elements inside the string since the order was different on Python 2 and 3. Replaced deprecated failIf with assertFalse.