Use pytest>=3.6.0

Hopefully prevents issue with Travis and timeout plugin compatibility

.travis.yml

@@ -22,7 +22,7 @@ install:
   - pip install flake8
 
 script:
-  - "pip install pytest pytest-timeout"
+  - "pip install pytest-timeout"
   - if [[ "${VIA}" == "compile" ]]; then python -m pytest --tb=native spacy; fi
   - if [[ "${VIA}" == "flake8" ]]; then flake8 . --count --exclude=spacy/compat.py,spacy/lang --select=E901,E999,F821,F822,F823 --show-source --statistics; fi
   - if [[ "${VIA}" == "pypi_nightly" ]]; then python -m pytest --tb=native --models --en `python -c "import os.path; import spacy; print(os.path.abspath(os.path.dirname(spacy.__file__)))"`; fi

requirements.txt

@@ -10,5 +10,5 @@ ujson>=1.35
 dill>=0.2,<0.3
 regex==2017.4.5
 requests>=2.13.0,<3.0.0
-pytest>=3.0.6,<4.0.0
+pytest>=3.6.0,<4.0.0
 mock>=2.0.0,<3.0.0