Actually fix travis builds

.travis.yml

@@ -8,9 +8,8 @@ python:
   - '3.4'
   - '3.5'
   - '3.6'
-  - 'nightly'
 
 install:
-  - pip install --user -U pip
+  - pip install -U pip setuptools pytest
 
 script: 'python setup.py test'

setup.py

@@ -32,8 +32,8 @@ setup(
     install_requires=requirements,
     extras_require=extras_require,
     test_suite='tests',
-    setup_requires=['pytest-runner'],
-    tests_require=['pytest', 'pytest-benchmark==3.1.0a2'],
+    setup_requires=['pytest-runner==2.11.1'],
+    tests_require=['pytest==3.1.3', 'pytest-benchmark==3.1.0a2'],
     classifiers=[
         'Development Status :: 4 - Beta',
         'License :: OSI Approved :: MIT License',