Include import of __future__ features division, absolute_imports and print_function everywhere. Don't add unicode_literals yet for it is harder to convert. Goal is smoothing the transition to python 3.
See 7a410f636b Command used: git grep -l 'Copyright 201'|xargs sed -i -E 's/Copyright 201./Copyright 2015/'`
7a410f636b
Conflicts: beets/library.py