When run on Python 3, linters such as Pylint and Flake8 will correctly flag __unicode__ and __long__ as _undefined names_ because _compat.py does not currently follow the Python porting best practice [___use feature detection instead of version detection___](https://docs.python.org/3/howto/pyporting.html#use-feature-detection-instead-of-version-detection). This PR allows this project to pass those tests without adding any linter directives.
See: https://www.python.org/dev/peps/pep-0519/
This is mostly encountered with pathlib in python 3, but this API
suggests any PathLike object can be treated like a filepath with
`__fspath__` function.
removed init_jinja_globals hack from app.py after consulting mitsuhiko
(didn't work on py 3.3 "as is")
removed with_statement future imports, not needed any more
needs more work on 2.7 as well as on 3.3
