Add separate lint stage in travis

.travis.yml

 language: python
 
 stages:
+  - lint
   - test
   - name: publish
     if: tag =~ ^\d+\.\d+\.\d+$
@@ -10,6 +11,14 @@ install:
 
 jobs:
   include:
+    - python: 2.7
+      stage: lint
+      script: tox -e flake8
+
+    - python: 3.4
+      stage: lint
+      script: tox -e flake8
+
     - python: 2.7
       stage: test
       script: tox -e py27
@@ -18,9 +27,6 @@ jobs:
       stage: test
       script: tox -e py34
 
-    - python: 3.4
-      script: tox -e flake8
-
     - stage: publish
       script: skip
       python: 2.7