2to3: Put `from __future__ import division in every python file.

This should be harmless, as we already are division clean. However,
placement of this import takes some care. In the future a script
can be used to append new features without worry, at least until
such time as it exceeds a single line. Having that ability will
make it easier to deal with absolute imports and printing updates.
MAINT: Make numpy/f2py/crackfortran docstring read better.

The copyright and short summary were moved to the top of the
docstring with the usage description below.
Merge pull request #3026 from charris/2to3-fix-print

2to3: Put `from __future__ import division` in every python file.