TST: switch from 3.6-dev to 3.6

Author: tacaswell

.travis.yml

@@ -64,8 +64,8 @@ matrix:
       env: BUILD_DOCS=true
     - python: 3.5
       env: USE_PYTEST=true PANDAS=pandas DELETE_FONT_CACHE=1 TEST_ARGS=
-    - python: "3.6-dev"
-      env: PRE=--pre
+    - python: 3.6
+      env: USE_PYTEST=true DELETE_FONT_CACHE=1 TEST_ARGS=
     - python: "nightly"
       env: PRE=--pre
     - os: osx