Make setup.py test use pytest #395

Done following the instructions from:

  https://pypi.org/project/pytest-runner

Fixes #394

Author: mhinz

setup.cfg

@@ -1,3 +1,6 @@
+[aliases]
+test = pytest
+
 [flake8]
 ignore = D211,E731,D401,W503
 

setup.py

@@ -8,6 +8,10 @@
     'msgpack>=0.5.0',
 ]
 
+setup_requires = [
+    'pytest-runner'
+]
+
 tests_require = [
     'pytest>=3.4.0',
 ]
@@ -40,6 +44,7 @@
                 'pynvim.msgpack_rpc.event_loop', 'pynvim.plugin',
                 'neovim', 'neovim.api'],
       install_requires=install_requires,
+      setup_requires=setup_requires,
       tests_require=tests_require,
       extras_require=extras_require,
       zip_safe=False)