Remove the `from __future__ import unicode_literals, print_function`.

[eldipa]

Describe the feature you'd like
Because byexample runs on Python 3 only, these __future__ imports (unicode_literals and print_function) are not needed anymore as they are the default.
Removing them will make the code a little cleaner.

When removing the imports from the examples/test, extra care should be taken to not break them or to hide some under-testing thing.