travis: Integrate the 'tox-travis' plugin

This allows us to greatly simplify the '.travis.yml' file and eventually
remove even more Makefile targets. This involves adding two new targets
to the list of default targets run by tox - docs and mypy - and adding
an addition 'travis' section per the 'tox-travis' docs [1]

[1] https://tox-travis.readthedocs.io/en/stable/toxenv.html#advanced-configuration

Signed-off-by: Stephen Finucane <stephen@that.guru>

.travis.yml

@@ -4,45 +4,30 @@ dist: trusty
 cache:
   directories:
     - $HOME/.cache/pip
+
 python:
   - "pypy-5.4.1"
   - "3.6"
   - "3.5"
   - "3.4"
   - "2.7"
   - "nightly"
+
 env:
   global:
     - TEST='-v --durations 25'
     - PYTHONFAULTHANDLER=x
     - PYTHONWARNINGS=all
     - SKIP_LATEX_BUILD=1
-  matrix:
-    - DOCUTILS=0.13.1
-    - DOCUTILS=0.14
-matrix:
-  exclude:
-    - python: "3.4"
-      env: DOCUTILS=0.13.1
-    - python: "3.5"
-      env: DOCUTILS=0.13.1
-    - python: "3.6"
-      env: DOCUTILS=0.13.1
-    - python: nightly
-      env: DOCUTILS=0.13.1
-    - python: "pypy-5.4.1"
-      env: DOCUTILS=0.13.1
+
 addons:
   apt:
     packages:
       - graphviz
       - imagemagick
+
 install:
-  - pip install -U pip setuptools
-  - pip install docutils==$DOCUTILS
-  - pip install -r test-reqs.txt
-  - if [[ $TRAVIS_PYTHON_VERSION == '3.6' ]]; then python3.6 -m pip install mypy typed-ast; fi
+  - pip install tox-travis
+
 script:
-  - flake8
-  - if [[ $TRAVIS_PYTHON_VERSION == '3.6' ]]; then make type-check test-async; fi
-  - if [[ $TRAVIS_PYTHON_VERSION != '3.6' ]]; then make test; fi
+  - tox

tox.ini

@@ -1,5 +1,12 @@
 [tox]
-envlist=flake8,py27,py34,py35,py36,pypy,du14,du13,du12,du11
+envlist=docs,flake8,mypy,py27,py34,py35,py36,pypy,du14,du13,du12,du11
+
+[travis]
+python =
+    2.7: py27, flake8, docs
+    3.4: py34, du11, du12, du13, du14
+    3.5: py35, mypy
+    3.6: py36
 
 [testenv]
 passenv = https_proxy http_proxy no_proxy
@@ -16,7 +23,6 @@ setenv =
     PYTHONDONTWRITEBYTECODE = true
 commands=
     {envpython} -Wall tests/run.py --ignore tests/py35 --cov=sphinx {posargs}
-    sphinx-build -q -W -b html -d {envtmpdir}/doctrees doc {envtmpdir}/html
 
 [testenv:flake8]
 deps=flake8
@@ -41,7 +47,6 @@ deps=
     {[testenv]deps}
 commands=
     {envpython} -Wall tests/run.py --cov=sphinx {posargs}
-    sphinx-build -q -W -b html -d {envtmpdir}/doctrees doc {envtmpdir}/html
 
 [testenv:mypy]
 deps=