Revert "Speed up Travis by reusing pip wheel cache across builds (#324)"

This reverts commit 47e689a89b.

.travis.yml

@@ -7,13 +7,7 @@ python:
 
 # Executed for 3.5 AND 3.5 as the first "test" stage:
 script:
-  - pip install -U pip wheel
-  - pip install .[test]
-  - pytest
-
-cache:
-    directories:
-        - $HOME/.cache/pip
+  - python setup.py test
 
 # This defines further stages that execute after the tests
 jobs:

setup.py

@@ -47,15 +47,10 @@ setup(
         datasette=datasette.cli:cli
     ''',
     setup_requires=['pytest-runner'],
-    extras_require={
-        'test': [
-            'pytest==3.6.0',
-            'aiohttp==2.3.2',
-            'beautifulsoup4==4.6.0',
-        ]
-    },
     tests_require=[
-        'datasette[test]',
+        'pytest==3.6.0',
+        'aiohttp==2.3.2',
+        'beautifulsoup4==4.6.0',
     ],
     classifiers=[
         'Development Status :: 4 - Beta',