Use package_data configuration option

Currently the uploaded tarball for benchcab v4.0.0 is missing the
site-packages/benchcab/data directory (see
https://anaconda.org/accessnri/benchcab/files). This change fixes this
by replacing the include_package_data option with the package_data
option in setup.cfg (see Data Files Support).

Conda package deployment was tested here in a forked repository and the
uploaded tarball contains the package data directory.

Fixes #267

setup.cfg

@@ -18,8 +18,10 @@ console_scripts =
 [tool:pytest]
 addopts = --doctest-modules --doctest-glob='*.rst' --ignore setup.py --ignore conftest.py --ignore docs/conf.py
 
-[options]
-include_package_data = True
+[options.package_data]
+benchcab =
+    data/*
+    data/test/*
 
 [versioneer]
 VCS = git