yamllint depends on pkg_resources.load_entry_point from setuptools to
make its command working, so this runtime dependency to setuptools is
necessary to be listed.
Move setuptools' packaging configuration from setup.py to setup.cfg to
simplify setup.py and make its packaging more dedeclarative.
Signed-off-by: Satoru SATOH <satoru.satoh@gmail.com>
By releasing as a [Python wheel](http://pythonwheels.com/) as well as a
source distribution, you can speed up end user’s installs. After merging
this command, to release you just need to run `python setup.py clean
sdist bdist_wheel upload`.
