Refactor tox.ini to test with sklearn 0.17 and 0.18

Author: dukebody

tox.ini

@@ -1,19 +1,19 @@
 [tox]
-envlist = py27, py34
+envlist = {py27,py35}-sklearn{17,18}
 
 [testenv]
 deps =
-    pip==7.0.1
-    pytest==2.7.1
+    pytest==3.0.5
     setuptools==16.0
     wheel==0.24.0
     flake8==2.4.1
+    numpy==1.11.3
+    scipy==0.18.1
+    pandas==0.19.2
+    sklearn17: scikit-learn==0.17.1
+    sklearn18: scikit-learn==0.18.1
     py27: mock==1.3.0
 
 commands =
-    pip install numpy --no-index
-    pip install scipy --no-index
-    pip install pandas --no-index
-    pip install scikit-learn --no-index
     flake8 tests
     py.test