Fixed an error with unicode literals in template extension setup.py
Fixed an error with unicode literals in template extension setup.py

When a new extension is created using ./contrib/tools/generate_extension.py and
running 'python setup.py develop' an error "setup command: package_data must be
a dictionary mapping package names to lists of wildcard patterns" occurs. The
problem is caused by the setup.py file importing __future__ unicode literals
because Python2 setuptools expects a "str" for parsing package_data.

Testing Done:
Created a new extension and ran 'python setup.py develop' with no errors.

Reviewed at https://reviews.reviewboard.org/r/6704/

brennie/reviewboard,bkochendorfer/reviewboard,chipx86/reviewboard,KnowNo/reviewboard,KnowNo/reviewboard,bkochendorfer/reviewboard,reviewboard/reviewboard,sgallagher/reviewboard,chipx86/reviewboard,davidt/reviewboard,davidt/reviewboard,beol/reviewboard,beol/reviewboard,reviewboard/reviewboard,KnowNo/reviewboard,custode/reviewboard,bkochendorfer/reviewboard,sgallagher/reviewboard,custode/reviewboard,brennie/reviewboard,reviewboard/reviewboard,custode/reviewboard,chipx86/reviewboard,bkochendorfer/reviewboard,brennie/reviewboard,KnowNo/reviewboard,custode/reviewboard,chipx86/reviewboard,davidt/reviewboard,reviewboard/reviewboard,davidt/reviewboard,brennie/reviewboard,sgallagher/reviewboard,beol/reviewboard,sgallagher/reviewboard,beol/reviewboard