Revert "Use tox-travis for Travis/Tox integration"

This reverts commit 74567f7.

.travis.yml

@@ -1,10 +1,27 @@
 sudo: false
 language: python
-python:
-  - "2.7"
-  - "3.4"
-  - "3.5"
+
+# Run tox with python 3.5, but let _it_ build the envs for the various Python
+# versions (instead of Travis)
+python: 3.5
+
+env:
+  matrix:
+    - TOXENV=py27-piplatest
+    - TOXENV=py34-piplatest
+    - TOXENV=py35-piplatest
+    - TOXENV=py27-pip8
+    - TOXENV=py34-pip8
+    - TOXENV=py35-pip8
+    - TOXENV=py27-pip9
+    - TOXENV=py34-pip9
+    - TOXENV=py35-pip9
+    - TOXENV=flake8
+
 install:
-- travis_retry pip install tox-travis
+  - travis_retry pip install tox
+
 cache: pip
-script: tox --travis-after
+
+script:
+  - tox

tox.ini

@@ -9,7 +9,7 @@ deps =
     coverage
     pytest
 commands =
-    pip --version
+    python -c 'import pip; print("Using pip %s" % pip.__version__)'
     python -m coverage run --source piptools -m pytest --strict {posargs:tests/}
     python -m coverage report -m
     python -m coverage html
@@ -18,8 +18,3 @@ commands =
 basepython = python2.7
 deps = flake8
 commands = flake8 piptools tests --max-line-length=120
-
-[travis]
-python =
-  2.7: py27, flake8
-