Make the nikola script work with Buildout 2.1.0

Buildout generates scripts with patches to insert the locations of required eggs into sys.path.

The ``__future__`` import of ``print_function`` ends up in the middle of the
script generated by Buildout, and causes errors at execution time. This can be seen in [the resulting script file](https://gist.github.com/kamitchell/5477735).

Since there are no print statements in this file, the ``__future__`` import
isn't necessary, so its removal should not cause any problems.

There's a pending fix on Buildout's end as their pull request buildout/buildout#112, but it hasn't made it to a release yet.